CVE-2026-27857
Citrix Gateway Stack-Based Buffer Overflow
Description
Sending "NOOP (((...)))" command with 4000 parenthesis open+close results in ~1MB extra memory usage. Longer commands will result in client disconnection. This 1 MB can be left allocated for longer time periods by not sending the command ending LF. So attacker could connect possibly from even a single IP and create 1000 connections to allocate 1 GB of memory, which would likely result in reaching VSZ limit and killing the process and its other proxied connections. Attacker could connect possibly from even a single IP and create 1000 connections to allocate 1 GB of memory, which would likely result in reaching VSZ limit and killing the process and its other proxied connections. Install fixed version, there is no other remediation. No publicly available exploits are known.
INFO
Published Date :
March 27, 2026, 9:16 a.m.
Last Modified :
June 30, 2026, 3:17 a.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | MEDIUM | 8ce71d90-2354-404b-a86e-bec2cc4e6981 | ||||
| CVSS 3.1 | MEDIUM | [email protected] | ||||
| CVSS 3.1 | HIGH | [email protected] | ||||
| CVSS 3.1 | HIGH | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c |
Solution
- Install the vendor-supplied fixed version.
- Update the affected software immediately.
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-2026-27857.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-27857 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-2026-27857
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-2026-27857 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-27857 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
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:rhel_els:7'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux Server Optional (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', 'cpe:/o:redhat:enterprise_linux:10.2'], '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_eus:10.0'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:10.1', 'cpe:/o:redhat:enterprise_linux:10.2'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux CodeReady Linux Builder (v. 10)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:enterprise_linux:8::crb'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux CRB (v. 8)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_eus:9.4::crb'], 'vendor': 'Red Hat', 'product': 'Red Hat CodeReady Linux Builder EUS (v.9.4)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:rhel_eus:9.6::crb'], 'vendor': 'Red Hat', 'product': 'Red Hat CodeReady Linux Builder EUS (v.9.6)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:enterprise_linux:9::crb'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux CodeReady Linux Builder (v. 9)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:6'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 6', 'defaultStatus': 'affected'}] Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added CWE CWE-770 Added Reference https://access.redhat.com/errata/RHSA-2026:13498 Added Reference https://access.redhat.com/errata/RHSA-2026:13830 Added Reference https://access.redhat.com/errata/RHSA-2026:13857 Added Reference https://access.redhat.com/errata/RHSA-2026:17602 Added Reference https://access.redhat.com/errata/RHSA-2026:17625 Added Reference https://access.redhat.com/errata/RHSA-2026:17626 Added Reference https://access.redhat.com/errata/RHSA-2026:17628 Added Reference https://access.redhat.com/errata/RHSA-2026:17630 Added Reference https://access.redhat.com/errata/RHSA-2026:18053 Added Reference https://access.redhat.com/errata/RHSA-2026:19149 Added Reference https://access.redhat.com/errata/RHSA-2026:19364 Added Reference https://access.redhat.com/errata/RHSA-2026:19453 Added Reference https://access.redhat.com/errata/RHSA-2026:19455 Added Reference https://access.redhat.com/errata/RHSA-2026:26564 Added Reference https://access.redhat.com/security/cve/CVE-2026-27857 Added Reference https://bugzilla.redhat.com/show_bug.cgi?id=2452179 Added Reference https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-27857.json -
CVE Modified by [email protected]
Jun. 17, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'Open-Xchange GmbH', 'modules': ['core'], 'product': 'OX Dovecot Pro', 'versions': [{'status': 'affected', 'version': '0', 'versionType': 'semver', 'lessThanOrEqual': '2.3.0'}], 'defaultStatus': 'unaffected'}] -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jun. 17, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-27857', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-03-27T12:39:00.311649Z'} -
Initial Analysis by [email protected]
Apr. 30, 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:dovecot:dovecot:*:*:*:*:*:*:*:* versions up to (excluding) 2.4.3 *cpe:2.3:a:open-xchange:dovecot:*:*:*:*:pro:*:*:* versions from (including) 3.0.0 up to (excluding) 3.0.5 *cpe:2.3:a:open-xchange:dovecot:*:*:*:*:pro:*:*:* versions from (including) 3.1.0 up to (excluding) 3.1.4 *cpe:2.3:a:open-xchange:dovecot:*:*:*:*:pro:*:*:* versions up to (excluding) 2.3.22.1 Added Reference Type Open-Xchange: https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0001.json Types: Vendor Advisory -
New CVE Received by [email protected]
Mar. 27, 2026
Action Type Old Value New Value Added Description Sending "NOOP (((...)))" command with 4000 parenthesis open+close results in ~1MB extra memory usage. Longer commands will result in client disconnection. This 1 MB can be left allocated for longer time periods by not sending the command ending LF. So attacker could connect possibly from even a single IP and create 1000 connections to allocate 1 GB of memory, which would likely result in reaching VSZ limit and killing the process and its other proxied connections. Attacker could connect possibly from even a single IP and create 1000 connections to allocate 1 GB of memory, which would likely result in reaching VSZ limit and killing the process and its other proxied connections. Install fixed version, there is no other remediation. No publicly available exploits are known. Added CVSS V3.1 AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L Added CWE CWE-400 Added Reference https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0001.json