CVE-2026-11941: Cloudflare Quiche Use-after-free Vulnerability

MODERATE
Advisory Identifier: GHSA-mh64-ph39-mrc9
Share
CVSS 5.6
CWE-416
Published
Advisory Summary

CVE-2026-11941 is a MODERATE (CVSS 5.6) use-after-free vulnerability (CWE-416: Use After Free) affecting Cloudflare Quiche libraries in the crates.io ecosystem. The issue involves use-after-free in connection id iterator ffi functions. Remediation is available by upgrading affected packages to version 0.29.2.

CVE-2026-11941 at a Glance

CVE Identifier CVE-2026-11941
GHSA Identifier GHSA-mh64-ph39-mrc9
Severity MODERATE
CVSS v3.1 Base Score 5.6
CWE Classification CWE-416: Use After Free
Affected Product Cloudflare Quiche
Package Ecosystem crates.io
Published Date
Last Updated

Security Impact

CVSS: 5.6

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L).

Attack Vector Network (AV:N)
Attack Complexity High (AC:H)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality Low (C:L)
Integrity Low (I:L)
Availability Low (A:L)

How to Fix CVE-2026-11941

To remediate this vulnerability, upgrade all affected Cloudflare Quiche dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

quiche fixed: 0.29.2 
Upgrade quiche to 0.29.2
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for quiche

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-11941, inspect your project dependencies for Cloudflare Quiche:

inspect dependencies for quiche

Analyze the terminal output to locate any version of Cloudflare Quiche in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.29.2), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-416: Use After Free, where the product reuses or references memory after it has been freed. at some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer. In Cloudflare Quiche, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Impact Cloudflare Quiche was affected by 2 use-after-free vulnerabilities in the connection ID iterator FFI functions. The `quiche_connection_id_iter_next` and `quiche_conn_retired_scid_next` functions would return a pointer to a `ConnectionId` to the applications via function arguments, but the the owned `ConnectionId` would be dropped at the end of those functions' scope. Only applications using those FFI functions are affected. The FFI API is disabled by default by a build-time feature flag. quiche 0.29.2 is the earliest version containing the fix for this issue.

CVE-2026-11941 Affected Cloudflare Quiche Versions

1 component(s)
Fixed Versions:
0.29.2
Product / Package Ecosystem Affected Versions Fixed Version
quiche
 crates.io
≥ 0.20.0
< 0.29.2
0.29.2

References

GitHub Advisory / Wiki ADVISORY
https://github.com/cloudflare/quiche/security/advisories/GHSA-mh64-ph39-mrc9
NVD — CVE-2026-11941 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-11941
Cloudflare Quiche Source Repository REPOSITORY
https://github.com/cloudflare/quiche

Frequently Asked Questions

What is CVE-2026-11941?
CVE-2026-11941 is a security vulnerability in Cloudflare Quiche involving Use-after-free in connection ID iterator FFI functions under CWE-416: Use After Free.
Which Cloudflare Quiche versions are affected?
Affected versions include releases prior to 0.29.2 across affected packages: quiche.
What version fixes CVE-2026-11941?
Upgrading to 0.29.2 (or the latest patched release for your respective branch) resolves the vulnerability.
Is quiche affected?
Yes, quiche is affected in releases prior to 0.29.2. Upgrade your dependency to 0.29.2 or later.
What is the CVSS score of CVE-2026-11941?
CVE-2026-11941 has a CVSS v3.1 base score of 5.6 (MODERATE) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L.
What CWE is associated with CVE-2026-11941?
CVE-2026-11941 is classified under CWE-416: Use After Free (The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.).
How can I check crates.io dependencies for CVE-2026-11941?
Run the dependency tree command: 'inspect dependencies for quiche'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-mh64-ph39-mrc9",
  "modified" : "2026-06-19T22:10:29Z",
  "published" : "2026-06-19T22:10:29Z",
  "aliases" : [ "CVE-2026-11941" ],
  "summary" : "Cloudflare Quiche: Use-after-free in connection ID iterator FFI functions",
  "details" : "### Impact\n\nCloudflare Quiche was affected by 2 use-after-free vulnerabilities in the connection ID iterator FFI functions.\n\nThe `quiche_connection_id_iter_next` and `quiche_conn_retired_scid_next` functions would return a pointer to a `ConnectionId` to the applications via function arguments, but the the owned `ConnectionId` would be dropped at the end of those functions' scope.\n\nOnly applications using those FFI functions are affected. The FFI API is disabled by default by a build-time feature flag.\n\nquiche 0.29.2 is the earliest version containing the fix for this issue.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "quiche"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.20.0"
      }, {
        "fixed" : "0.29.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/cloudflare/quiche/security/advisories/GHSA-mh64-ph39-mrc9"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-11941"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/cloudflare/quiche"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-416" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-19T22:10:29Z",
    "nvd_published_at" : "2026-06-19T12:16:26Z"
  }
}