nghttp2 Denial of service: Assertion failure due to the missing state validation

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Summary

CVECVE-2026-27135
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-03-18 18:16:26 UTC
Updated2026-05-13 22:16:42 UTC
Descriptionnghttp2 is an implementation of the Hypertext Transfer Protocol version 2 in C. Prior to version 1.68.1, the nghttp2 library stops reading the incoming data when user facing public API `nghttp2_session_terminate_session` or `nghttp2_session_terminate_session2` is called by the application. They might be called internally by the library when it detects the situation that is subject to connection error. Due to the missing internal state validation, the library keeps reading the rest of the data after one of those APIs is called. Then receiving a malformed frame that causes FRAME_SIZE_ERROR causes assertion failure. nghttp2 v1.68.1 adds missing state validation to avoid assertion failure. No known workarounds are available.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS: 0.000240000 probability, percentile 0.069560000 (date 2026-05-13)

Problem Types: CWE-617 | CWE-617 CWE-617: Reachable Assertion

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1CNADECLARED7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Nghttp2 Nghttp2 All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Nghttp2 Nghttp2 affected < 1.68.1 Not specified

References

ReferenceSourceLinkTags
github.com/nghttp2/nghttp2/commit/5c7df8fa815ac1004d9ecb9d1f7595c4d37f46e1 [email protected] github.com Patch
www.openwall.com/lists/oss-security/2026/03/20/3 af854a3a-2127-422b-91ae-364da2661108 www.openwall.com Mailing List, Third Party Advisory
github.com/nghttp2/nghttp2/security/advisories/GHSA-6933-cjhr-5qg6 [email protected] github.com Patch, Vendor Advisory
lists.debian.org/debian-lts-announce/2026/05/msg00025.html af854a3a-2127-422b-91ae-364da2661108 lists.debian.org
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