Description
CivetWeb through 1.16, when built with USE_HTTP2 and enable_http2 on, contains a use-after-free vulnerability in handle_http2() that retains freed :method and :path pointers. Unauthenticated remote attackers can send a later HEADERS frame omitting these pseudo-headers to influence request method or path seen by access rules, or crash the server.
Published: 2026-11-06
Score: 9.2 Critical
EPSS: n/a
KEV: No
Impact: Denial of Service or Access Control Bypass
Action: Immediate Patch
AI Analysis

Impact

CivetWeb through version 1.16 contains a use‑after‑free bug in the HTTP/2 request handler. When the server is built with USE_HTTP2 and HTTP/2 is enabled, freed pointers for the :method and :path pseudo‑headers are left unresolved. An unauthenticated attacker can later send a HEADERS frame that omits these pseudo‑headers, causing the server to use stale memory to determine the request method or path. This can either crash the server, resulting in denial of service, or alter the request in a way that bypasses configured access rules, potentially allowing unauthorized operations.

Affected Systems

The vulnerability affects CivetWeb 1.16 and earlier releases that are compiled with the USE_HTTP2 flag and have HTTP/2 enabled. Any deployment of CivetWeb running an affected binary and accepting HTTP/2 connections is susceptible; newer releases that have applied the fix are not impacted.

Risk and Exploitability

The CVSS score of 9.2 indicates critical risk. Although EPSS is not available and the issue is not listed in CISA KEV, the vulnerability is exploitable remotely without authentication over HTTP/2, making it highly attractive to attackers. Because the flaw permits server crashes or manipulation of request metadata, it can lead to service disruption or security bypasses. Immediate patching or mitigation is strongly advised.

Generated by OpenCVE AI on November 6, 2026 at 21:05 UTC.

Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

  • Upgrade CivetWeb to a version that includes the HTTP/2 use‑after‑free fix.
  • If upgrading is not immediately possible, configure the server to disable HTTP/2 by setting enable_http2 to false or removing the USE_HTTP2 compile flag.
  • When disabling HTTP/2 is not feasible, consider blocking or limiting HTTP/2 traffic at the network perimeter to reduce exposure.

Generated by OpenCVE AI on November 6, 2026 at 21:05 UTC.

Tracking

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Advisories

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History

Fri, 06 Nov 2026 19:30:00 +0000

Type Values Removed Values Added
Description CivetWeb through 1.16, when built with USE_HTTP2 and enable_http2 on, contains a use-after-free vulnerability in handle_http2() that retains freed :method and :path pointers. Unauthenticated remote attackers can send a later HEADERS frame omitting these pseudo-headers to influence request method or path seen by access rules, or crash the server.
Title CivetWeb through 1.16 HTTP/2 Use-After-Free via Stale Pseudo-Header State
First Time appeared Civetweb Project
Civetweb Project civetweb
Weaknesses CWE-416
CPEs cpe:2.3:a:civetweb_project:civetweb:*:*:*:*:*:*:*:*
Vendors & Products Civetweb Project
Civetweb Project civetweb
References
Metrics cvssV3_1

{'score': 8.1, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H'}

cvssV4_0

{'score': 9.2, 'vector': 'CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N'}

Subscriptions

Civetweb Project Civetweb
cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published:

Updated: 2026-11-06T19:14:48.975Z

Reserved: 2026-11-06T19:11:14.928Z

Link: CVE-2026-124040

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Deferred

Published: 2026-11-06T20:17:22.203

Modified: 2026-11-06T20:17:22.347

Link: CVE-2026-124040

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-11-06T21:45:10Z

Weaknesses