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7.5
HIGH CVSS 3.1
CVE-2026-40170
ngtcp2 has a qlog transport parameter serialization stack buffer overflow
Overview
Description

ngtcp2 is a C implementation of the IETF QUIC protocol. In versions prior to 1.22.1, ngtcp2_qlog_parameters_set_transport_params() serializes peer transport parameters into a fixed 1024-byte stack buffer without bounds checking. When qlog is enabled, a remote peer can send sufficiently large transport parameters during the QUIC handshake to cause writes beyond the buffer boundary, resulting in a stack buffer overflow. This affects deployments that enable the qlog callback and process untrusted peer transport parameters. This issue has been fixed in version 1.22.1. If developers are unable to immediately upgrade, they can disable the qlog on client.

Details
INFO

Published Date :

April 16, 2026, 10:16 p.m.

Last Modified :

July 15, 2026, 2:21 a.m.

Remotely Exploit :

Yes !

Source :

[email protected]
Impact
Affected Products

The following products are affected by CVE-2026-40170 vulnerability. Even if cvefeed.io is aware of the exact versions of the products that are affected, the information is not represented in the table below.

ID Vendor Product Action
1 Nghttp2 ngtcp2
1 Tatsuhiro-t ngtcp2
: Total Affected Vendor : 2 | Products : 2
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 MITRE-CVE
CVSS 3.1 HIGH 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Solution
Update ngtcp2 to version 1.22.1 to fix stack buffer overflow.
  • Update ngtcp2 to version 1.22.1.
  • Disable qlog if unable to update immediately.
Public PoC/Exploit Available at Github

CVE-2026-40170 has a 1 public PoC/Exploit available at Github. Go to the Public Exploits tab to see the list.

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-2026-40170.

URL Resource
https://github.com/ngtcp2/ngtcp2/commit/708a7640c1f48fb8ffb540c4b8ea5b4c1dfb8ee5 Patch
https://github.com/ngtcp2/ngtcp2/security/advisories/GHSA-f523-465f-8c8f Exploit Mitigation Patch Vendor Advisory
http://www.openwall.com/lists/oss-security/2026/04/17/12 Exploit Mailing List Mitigation Patch Third Party Advisory
https://access.redhat.com/errata/RHSA-2026:22963
https://access.redhat.com/errata/RHSA-2026:25049
https://access.redhat.com/errata/RHSA-2026:9113
https://access.redhat.com/security/cve/CVE-2026-40170
https://bugzilla.redhat.com/show_bug.cgi?id=2459061
https://github.com/ngtcp2/ngtcp2/security/advisories/GHSA-f523-465f-8c8f Exploit Mitigation Patch Vendor Advisory
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40170.json
CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorizes the common flaws or weaknesses that can lead to vulnerabilities. CVE-2026-40170 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-2026-40170 weaknesses.

CAPEC-8: Buffer Overflow in an API Call Buffer Overflow in an API Call CAPEC-9: Buffer Overflow in Local Command-Line Utilities Buffer Overflow in Local Command-Line Utilities CAPEC-10: Buffer Overflow via Environment Variables Buffer Overflow via Environment Variables CAPEC-14: Client-side Injection-induced Buffer Overflow Client-side Injection-induced Buffer Overflow CAPEC-24: Filter Failure through Buffer Overflow Filter Failure through Buffer Overflow CAPEC-42: MIME Conversion MIME Conversion CAPEC-44: Overflow Binary Resource File Overflow Binary Resource File CAPEC-45: Buffer Overflow via Symbolic Links Buffer Overflow via Symbolic Links CAPEC-46: Overflow Variables and Tags Overflow Variables and Tags CAPEC-47: Buffer Overflow via Parameter Expansion Buffer Overflow via Parameter Expansion CAPEC-67: String Format Overflow in syslog() String Format Overflow in syslog() CAPEC-92: Forced Integer Overflow Forced Integer Overflow CAPEC-100: Overflow Buffers Overflow Buffers

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).

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arise-ai-security/arise-sec-lion

None

Python Dockerfile Jinja JavaScript HTML TypeScript CSS Shell

Updated: 1 week, 1 day ago
2 stars 0 fork 0 watcher
Born at : Nov. 18, 2025, 12:35 a.m. This repo has been linked 7 different CVEs too.

Results are limited to the first 15 repositories due to potential performance issues.

The following list is the news that have been mention CVE-2026-40170 vulnerability anywhere in the article.

Results are limited to the first 20 news articles due to potential performance issues.

The following table lists the changes that have been made to the CVE-2026-40170 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:enterprise_linux:10.2'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream (v. 10)', '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:10.2'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux BaseOS (v. 10)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:9::baseos'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux BaseOS (v. 9)', 'defaultStatus': 'affected'}, {'cpes': ['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:9::crb'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux CodeReady Linux Builder (v. 9)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:hummingbird:1'], 'vendor': 'Red Hat', 'product': 'Red Hat Hardened Images', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:enterprise_linux:9::resilientstorage'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux Resilient Storage (v. 9)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:10'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 10', 'defaultStatus': 'unaffected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:8'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 8', 'defaultStatus': 'unaffected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:9'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 9', 'defaultStatus': 'unaffected'}] [{'cpes': ['cpe:/o:redhat:enterprise_linux:10.2'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 10', 'versions': [{'status': 'unaffected', 'version': '0:4.23.5-109.el10_2', 'lessThan': '*', 'versionType': 'rpm'}], 'packageName': 'samba', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:enterprise_linux:9', 'cpe:/o:redhat:enterprise_linux:9'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 9', 'versions': [{'status': 'unaffected', 'version': '0:4.23.5-10.el9_8', 'lessThan': '*', 'versionType': 'rpm'}], 'packageName': 'samba', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:hummingbird:1'], 'vendor': 'Red Hat', 'product': 'Red Hat Hardened Images', 'versions': [{'status': 'unaffected', 'version': '1.22.1-1.hum1', 'lessThan': '*', 'versionType': 'rpm'}], 'packageName': 'ngtcp2-main', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:10'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 10', 'packageName': 'nodejs22', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'unaffected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:10'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 10', 'packageName': 'nodejs24', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'unaffected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:8'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 8', 'packageName': 'nodejs', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'unaffected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:8'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 8', 'packageName': 'nodejs:20/nodejs', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'unaffected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:8'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 8', 'packageName': 'nodejs:22/nodejs', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'unaffected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:8'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 8', 'packageName': 'nodejs:24/nodejs', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'unaffected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:9'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 9', 'packageName': 'nodejs', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'unaffected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:9'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 9', 'packageName': 'nodejs:20/nodejs', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'unaffected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:9'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 9', 'packageName': 'nodejs:22/nodejs', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'unaffected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:9'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 9', 'packageName': 'nodejs:24/nodejs', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'unaffected'}]
  • CVE Modified by 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

    Jun. 30, 2026

    Action Type Old Value New Value
    Added Affected [{'cpes': ['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:9::appstream'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux AppStream (v. 9)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:10.2'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux BaseOS (v. 10)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:9::baseos'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux BaseOS (v. 9)', 'defaultStatus': 'affected'}, {'cpes': ['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:9::crb'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux CodeReady Linux Builder (v. 9)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:hummingbird:1'], 'vendor': 'Red Hat', 'product': 'Red Hat Hardened Images', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:enterprise_linux:9::resilientstorage'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux Resilient Storage (v. 9)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:10'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 10', 'defaultStatus': 'unaffected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:8'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 8', 'defaultStatus': 'unaffected'}, {'cpes': ['cpe:/o:redhat:enterprise_linux:9'], 'vendor': 'Red Hat', 'product': 'Red Hat Enterprise Linux 9', '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-120
    Added Reference https://access.redhat.com/errata/RHSA-2026:22963
    Added Reference https://access.redhat.com/errata/RHSA-2026:25049
    Added Reference https://access.redhat.com/errata/RHSA-2026:9113
    Added Reference https://access.redhat.com/security/cve/CVE-2026-40170
    Added Reference https://bugzilla.redhat.com/show_bug.cgi?id=2459061
    Added Reference https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40170.json
  • CVE Modified by [email protected]

    Jun. 17, 2026

    Action Type Old Value New Value
    Added Affected [{'vendor': 'ngtcp2', 'product': 'ngtcp2', 'versions': [{'status': 'affected', 'version': '< 1.22.1'}]}]
  • CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0

    Jun. 17, 2026

    Action Type Old Value New Value
    Added SSVC {'id': 'CVE-2026-40170', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'poc'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-04-17T14:52:12.292330Z'}
  • Reanalysis by [email protected]

    May. 22, 2026

    Action Type Old Value New Value
    Changed CPE Configuration OR *cpe:2.3:a:nghttp2:ngtcp2:*:*:*:*:*:*:*:* versions up to (excluding) 1.22.1 OR *cpe:2.3:a:tatsuhiro-t:ngtcp2:*:*:*:*:*:*:*:* versions up to (excluding) 1.22.1
  • Initial Analysis by [email protected]

    May. 21, 2026

    Action Type Old Value New Value
    Added CPE Configuration OR *cpe:2.3:a:nghttp2:ngtcp2:*:*:*:*:*:*:*:* versions up to (excluding) 1.22.1
    Added Reference Type GitHub, Inc.: https://github.com/ngtcp2/ngtcp2/commit/708a7640c1f48fb8ffb540c4b8ea5b4c1dfb8ee5 Types: Patch
    Added Reference Type GitHub, Inc.: https://github.com/ngtcp2/ngtcp2/security/advisories/GHSA-f523-465f-8c8f Types: Exploit, Mitigation, Patch, Vendor Advisory
    Added Reference Type CISA-ADP: https://github.com/ngtcp2/ngtcp2/security/advisories/GHSA-f523-465f-8c8f Types: Exploit, Mitigation, Patch, Vendor Advisory
    Added Reference Type CVE: http://www.openwall.com/lists/oss-security/2026/04/17/12 Types: Exploit, Mailing List, Mitigation, Patch, Third Party Advisory
  • CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0

    Apr. 20, 2026

    Action Type Old Value New Value
    Added Reference https://github.com/ngtcp2/ngtcp2/security/advisories/GHSA-f523-465f-8c8f
  • CVE Modified by af854a3a-2127-422b-91ae-364da2661108

    Apr. 17, 2026

    Action Type Old Value New Value
    Added Reference http://www.openwall.com/lists/oss-security/2026/04/17/12
  • New CVE Received by [email protected]

    Apr. 16, 2026

    Action Type Old Value New Value
    Added Description ngtcp2 is a C implementation of the IETF QUIC protocol. In versions prior to 1.22.1, ngtcp2_qlog_parameters_set_transport_params() serializes peer transport parameters into a fixed 1024-byte stack buffer without bounds checking. When qlog is enabled, a remote peer can send sufficiently large transport parameters during the QUIC handshake to cause writes beyond the buffer boundary, resulting in a stack buffer overflow. This affects deployments that enable the qlog callback and process untrusted peer transport parameters. This issue has been fixed in version 1.22.1. If developers are unable to immediately upgrade, they can disable the qlog on client.
    Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
    Added CWE CWE-121
    Added Reference https://github.com/ngtcp2/ngtcp2/commit/708a7640c1f48fb8ffb540c4b8ea5b4c1dfb8ee5
    Added Reference https://github.com/ngtcp2/ngtcp2/security/advisories/GHSA-f523-465f-8c8f
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.
CVSS
Vulnerability Scoring Details
Base CVSS Score: 7.5
Attack Vector
Attack Complexity
Privileges Required
User Interaction
Scope
Confidentiality Impact
Integrity Impact
Availability Impact