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Vulnerability · CVE-2026-27135

nghttp2 is an implementation of the Hypertext Transfer Protocol version 2 in C.

Published Mar 18, 2026 · corrected/updated Oct 15, 2026 · Red Hat nghttp2 · evidence confidence high

nghttp2 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 or 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.

Grounded briefings

Catalog interpretations for three audiences. Each brief cites ingested metadata and the original advisories below. They are not independent research and they do not invent exploit steps.

Executive

CVE-2026-27135 is a high public vulnerability record for Red Hat nghttp2. It is not currently listed in the CISA Known Exploited catalog. Check the linked vendor or CERT advisories for patch status. This summary is a catalog interpretation of the ingested metadata and cites the original advisories below.

System administrator

Identify whether Red Hat nghttp2 is in your estate, then compare installed versions with the affected ranges. Affected packages or ranges on record: nghttp2/nghttp2. Check the linked vendor or CERT advisories for patch status. Prefer the vendor or distribution advisory linked in Sources before changing production systems. This is a catalog interpretation, not a runbook.

Security analyst

Signals on file: CVSS 7.5, EPSS 0.9%. It is not currently listed in the CISA Known Exploited catalog. Weakness classes: CWE-617. Sources contributing to this record: csaf, csaf, csaf, cve_org. Public exploit references, when present, are outbound links only and are not proof of active exploitation. This is a catalog interpretation of stored metadata.

Exploitation and remediation

  • Exploitation evidence

    Not listed as known exploited in CISA KEV. Not in CISA KEV or VulnCheck KEV.

  • Patch and remediation

    No required-action text is stored yet. Use the vendor or CERT links in Sources for patch availability.

  • Safe detection guidance

    Compare installed versions with the affected ranges below and verify the advisory from the original publisher. This site stores metadata and outbound links only; it does not ship exploit code or proof-of-concept payloads.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Mar 18, 2026 · NIST NVD

    Detected

    nghttp2 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 or 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 read

  2. Oct 15, 2026 · NIST NVD

    Updated

    nghttp2 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 or 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 read

Affected

  • cpe nghttp2/nghttp2version unspecified

Sources

  • CSAF AdvisoriesVendor advisoryRHSA-2026:9711:CVE-2026-27135

    A flaw was found in nghttp2. Due to missing internal state validation, the library continues to process incoming data even after a session has been terminated. A remote attacker could exploit this by sending a specially crafted HTTP/2 frame, leading to an assertion failure and a

    security.access.redhat.com
  • CSAF AdvisoriesVendor advisoryRHSA-2026:9832:CVE-2026-27135

    A flaw was found in nghttp2. Due to missing internal state validation, the library continues to process incoming data even after a session has been terminated. A remote attacker could exploit this by sending a specially crafted HTTP/2 frame, leading to an assertion failure and a

    security.access.redhat.com
  • CSAF AdvisoriesVendor advisoryRHSA-2026:9874:CVE-2026-27135

    A flaw was found in nghttp2. Due to missing internal state validation, the library continues to process incoming data even after a session has been terminated. A remote attacker could exploit this by sending a specially crafted HTTP/2 frame, leading to an assertion failure and a

    security.access.redhat.com
  • CVE.orgVulnerability recordCVE-2026-27135

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-27135

    30-day exploitation probability 0.9%

    first.org
  • NIST NVDVulnerability recordCVE-2026-27135

    nghttp2 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 or is called by the ap

    nvd.nist.gov

References