9.2
CRITICAL
CVSS 4.0
CVE-2026-33526
Squid vulnerable to Denial of Service in ICP Request handling
Overview
Description
Squid is a caching proxy for the Web. Prior to version 7.5, due to heap Use-After-Free, Squid is vulnerable to Denial of Service when handling ICP traffic. This problem allows a remote attacker to perform a reliable and repeatable Denial of Service attack against the Squid service using ICP protocol. This attack is limited to Squid deployments that explicitly enable ICP support (i.e. configure non-zero `icp_port`). This problem _cannot_ be mitigated by denying ICP queries using `icp_access` rules. Version 7.5 contains a patch.
Details
INFO
Published Date :
March 26, 2026, 1:16 a.m.
Last Modified :
July 15, 2026, 2:20 a.m.
Remotely Exploit :
Yes !
Source :
[email protected]
Scoring
CVSS Scores
The Common Vulnerability Scoring System is a standardized framework
for assessing the severity of vulnerabilities in software and systems.
We collect and displays CVSS scores from various sources for each CVE.
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | HIGH | [email protected] | ||||
| CVSS 3.1 | HIGH | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | ||||
| CVSS 4.0 | CRITICAL | [email protected] |
Solution
Update Squid to version 7.5 or later to fix a heap Use-After-Free vulnerability.
- Update Squid to version 7.5.
- Ensure ICP support is disabled if not needed.
- Apply vendor patches as they become available.
References
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-33526.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-33526 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-33526
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-33526 vulnerability anywhere in the article.
-
Daily CyberSecurity
Apache Traffic Server Patches “Double-Header” DoS and Request Smuggling Flaws
Apache Traffic Server, the high-performance web proxy cache responsible for keeping the modern web fast, is facing a double-header of security challenges. Trusted by ISPs and global enterprises to max ... Read more
Published Date:
Apr 03, 2026 (3 months, 2 weeks ago)
The following table lists the changes that have been made to the
CVE-2026-33526 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Modified by 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Jul. 15, 2026
Action Type Old Value New Value Changed Affected [{'cpes': ['cpe:/o:redhat:rhel_els:7'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux Server (v. 7 ELS)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux_eus:10.0'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream EUS (v. 10.0)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:10.1'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream (v. 10)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:enterprise_linux:8::appstream'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream (v. 8)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_aus:8.4::appstream'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream AUS (v.8.4)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_eus_long_life:8.4::appstream'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_aus:8.6::appstream'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream AUS (v.8.6)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_e4s:8.6::appstream'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream E4S (v.8.6)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_tus:8.6::appstream'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream TUS (v.8.6)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_e4s:8.8::appstream'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream E4S (v.8.8)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_tus:8.8::appstream'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream TUS (v.8.8)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_e4s:9.0::appstream'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream E4S (v.9.0)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_e4s:9.2::appstream'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream E4S (v.9.2)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_eus:9.4::appstream'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream EUS (v.9.4)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_eus:9.6::appstream'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream EUS (v.9.6)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:enterprise_linux:9::appstream'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream (v. 9)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:6'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 6', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:rhel_els:7'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux Server Optional (v. 7 ELS)', 'defaultStatus': 'unaffected'}] [{'cpes': ['cpe:/o:redhat:enterprise_linux:10.1'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 10', 'versions': [{'status': 'unaffected', 'version': '7:6.10-6.el10_1.3', 'lessThan': '*', 'versionType': 'rpm'}], 'packageName': 'squid', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux_eus:10.0'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 10.0 Extended Update Support', 'versions': [{'status': 'unaffected', 'version': '7:6.10-5.el10_0.2', 'lessThan': '*', 'versionType': 'rpm'}], 'packageName': 'squid', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:rhel_els:7'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 7 Extended Lifecycle Support', 'versions': [{'status': 'unaffected', 'version': '7:3.5.20-17.el7_9.16', 'lessThan': '*', 'versionType': 'rpm'}], 'packageName': 'squid', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:enterprise_linux:8'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 8', 'versions': [{'status': 'unaffected', 'version': '8100020260408092701.489197e6', 'lessThan': '*', 'versionType': 'rpm'}], 'packageName': 'squid:4', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_aus:8.4'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support', 'versions': [{'status': 'unaffected', 'version': '8040020260514123440.522a0ee4', 'lessThan': '*', 'versionType': 'rpm'}], 'packageName': 'squid:4', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_eus_long_life:8.4'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On', 'versions': [{'status': 'unaffected', 'version': '8040020260514123440.522a0ee4', 'lessThan': '*', 'versionType': 'rpm'}], 'packageName': 'squid:4', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_aus:8.6'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support', 'versions': [{'status': 'unaffected', 'version': '8060020260518090356.ad008a3a', 'lessThan': '*', 'versionType': 'rpm'}], 'packageName': 'squid:4', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_tus:8.6'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 8.6 Telecommunications Update Service', 'versions': [{'status': 'unaffected', 'version': '8060020260518090356.ad008a3a', 'lessThan': '*', 'versionType': 'rpm'}], 'packageName': 'squid:4', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_e4s:8.6'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 8.6 Update Services for SAP Solutions', 'versions': [{'status': 'unaffected', 'version': '8060020260518090356.ad008a3a', 'lessThan': '*', 'versionType': 'rpm'}], 'packageName': 'squid:4', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_tus:8.8'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 8.8 Telecommunications Update Service', 'versions': [{'status': 'unaffected', 'version': '8080020260514105733.63b34585', 'lessThan': '*', 'versionType': 'rpm'}], 'packageName': 'squid:4', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_e4s:8.8'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions', 'versions': [{'status': 'unaffected', 'version': '8080020260514105733.63b34585', 'lessThan': '*', 'versionType': 'rpm'}], 'packageName': 'squid:4', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:enterprise_linux:9'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 9', 'versions': [{'status': 'unaffected', 'version': '7:5.5-22.el9_7.4', 'lessThan': '*', 'versionType': 'rpm'}], 'packageName': 'squid', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_e4s:9.0'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 9.0 Update Services for SAP Solutions', 'versions': [{'status': 'unaffected', 'version': '7:5.2-1.el9_0.10', 'lessThan': '*', 'versionType': 'rpm'}], 'packageName': 'squid', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_e4s:9.2'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions', 'versions': [{'status': 'unaffected', 'version': '7:5.5-5.el9_2.11', 'lessThan': '*', 'versionType': 'rpm'}], 'packageName': 'squid', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_eus:9.4'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 9.4 Extended Update Support', 'versions': [{'status': 'unaffected', 'version': '7:5.5-13.el9_4.5', 'lessThan': '*', 'versionType': 'rpm'}], 'packageName': 'squid', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_eus:9.6'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 9.6 Extended Update Support', 'versions': [{'status': 'unaffected', 'version': '7:5.5-19.el9_6.3', 'lessThan': '*', 'versionType': 'rpm'}], 'packageName': 'squid', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:6'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 6', 'packageName': 'squid', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'unknown'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:6'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 6', 'packageName': 'squid34', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'unknown'}] -
CVE Modified by 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Jun. 30, 2026
Action Type Old Value New Value Added Affected [{'cpes': ['cpe:/o:redhat:rhel_els:7'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux Server (v. 7 ELS)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux_eus:10.0'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream EUS (v. 10.0)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:10.1'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream (v. 10)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:enterprise_linux:8::appstream'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream (v. 8)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_aus:8.4::appstream'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream AUS (v.8.4)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_eus_long_life:8.4::appstream'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_aus:8.6::appstream'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream AUS (v.8.6)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_e4s:8.6::appstream'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream E4S (v.8.6)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_tus:8.6::appstream'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream TUS (v.8.6)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_e4s:8.8::appstream'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream E4S (v.8.8)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_tus:8.8::appstream'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream TUS (v.8.8)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_e4s:9.0::appstream'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream E4S (v.9.0)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_e4s:9.2::appstream'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream E4S (v.9.2)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_eus:9.4::appstream'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream EUS (v.9.4)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_eus:9.6::appstream'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream EUS (v.9.6)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:enterprise_linux:9::appstream'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream (v. 9)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:6'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 6', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:rhel_els:7'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux Server Optional (v. 7 ELS)', 'defaultStatus': 'unaffected'}] Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added CWE CWE-825 Added Reference https://access.redhat.com/errata/RHSA-2026:10255 Added Reference https://access.redhat.com/errata/RHSA-2026:10256 Added Reference https://access.redhat.com/errata/RHSA-2026:10257 Added Reference https://access.redhat.com/errata/RHSA-2026:11901 Added Reference https://access.redhat.com/errata/RHSA-2026:20564 Added Reference https://access.redhat.com/errata/RHSA-2026:20565 Added Reference https://access.redhat.com/errata/RHSA-2026:20580 Added Reference https://access.redhat.com/errata/RHSA-2026:6301 Added Reference https://access.redhat.com/errata/RHSA-2026:8119 Added Reference https://access.redhat.com/errata/RHSA-2026:8317 Added Reference https://access.redhat.com/errata/RHSA-2026:8880 Added Reference https://access.redhat.com/errata/RHSA-2026:9220 Added Reference https://access.redhat.com/security/cve/CVE-2026-33526 Added Reference https://bugzilla.redhat.com/show_bug.cgi?id=2451574 Added Reference https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33526.json -
CVE Modified by [email protected]
Jun. 17, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'squid-cache', 'product': 'squid', 'versions': [{'status': 'affected', 'version': '< 7.5'}]}] -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jun. 17, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-33526', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-03-26T18:20:32.942486Z'} -
Initial Analysis by [email protected]
Mar. 31, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added CPE Configuration OR *cpe:2.3:a:squid-cache:squid:*:*:*:*:*:*:*:* versions up to (excluding) 7.5 Added Reference Type GitHub, Inc.: https://github.com/squid-cache/squid/commit/8a7d42f9d44befb8fcbbb619505587c8de6a1e91 Types: Patch Added Reference Type GitHub, Inc.: https://github.com/squid-cache/squid/security/advisories/GHSA-hpfx-h48q-gvwg Types: Vendor Advisory Added Reference Type CVE: http://www.openwall.com/lists/oss-security/2026/03/25/2 Types: Third Party Advisory -
CVE Modified by af854a3a-2127-422b-91ae-364da2661108
Mar. 26, 2026
Action Type Old Value New Value Added Reference http://www.openwall.com/lists/oss-security/2026/03/25/2 -
New CVE Received by [email protected]
Mar. 26, 2026
Action Type Old Value New Value Added Description Squid is a caching proxy for the Web. Prior to version 7.5, due to heap Use-After-Free, Squid is vulnerable to Denial of Service when handling ICP traffic. This problem allows a remote attacker to perform a reliable and repeatable Denial of Service attack against the Squid service using ICP protocol. This attack is limited to Squid deployments that explicitly enable ICP support (i.e. configure non-zero `icp_port`). This problem _cannot_ be mitigated by denying ICP queries using `icp_access` rules. Version 7.5 contains a patch. Added CVSS V4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CWE CWE-416 Added CWE CWE-826 Added Reference https://github.com/squid-cache/squid/commit/8a7d42f9d44befb8fcbbb619505587c8de6a1e91 Added Reference https://github.com/squid-cache/squid/security/advisories/GHSA-hpfx-h48q-gvwg
EPSS is a daily estimate of the probability of exploitation activity
being observed over the next 30 days. Following chart shows the EPSS
score history of the vulnerability.