# CVE-2026-11941: Use-after-free in connection ID iterator and FFI functions

> Applications using disabled-by-default FFI functions in Quiche may crash or leak memory due to use-after-free errors.

- **Severity:** Medium 5.6 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 19 Jun 2026
- **Updated:** 22 Jun 2026
- **Also known as:** GHSA-mh64-ph39-mrc9

## What is CVE-2026-11941?

CVE-2026-11941 is a medium-severity use after free vulnerability in Cloudflare Quiche, published on 19 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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 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.

Impact
If unpatched, an application calling the affected FFI functions will dereference freed memory. The most likely outcome is undefined behavior leading to a process crash (denial of service). Depending on allocator state, the read may also return adjacent heap contents, resulting in limited information disclosure or incorrect connection identifier handling.

Mitigation
Users are requested to upgrade to quiche 0.29.2 which is the earliest version containing the fix for this issue.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-11941?

2 open source packages ship an affected version, including quiche.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `quiche` | crates.io | From 0.20.0 | 0.29.2 |
| `quiche` | crates.io | From 0.20.0 | 0.29.2 |

## How do I fix CVE-2026-11941?

Upgrade quiche to 0.29.2 or later.

## Is CVE-2026-11941 being exploited?

There is no known exploitation of CVE-2026-11941 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-11941 and fix it if it is affected.

What it is: CVE-2026-11941 is a medium-severity use after free vulnerability in Cloudflare Quiche, published on 19 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-11941 in the wild and no public exploit code.

Affected packages and fixed versions:
- quiche (crates.io): affected from 0.20.0; fixed in 0.29.2
- quiche (crates.io): affected from 0.20.0; fixed in 0.29.2

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-11941/ (Markdown: https://insights.sbomify.com/CVE-2026-11941/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-11941
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-11941
- OSV: https://osv.dev/vulnerability/CVE-2026-11941

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-11941/
Summaries are generated and may contain mistakes; the official description above is the record.