# CVE-2025-40176: tls: wait for pending async decryptions if tls_strp_msg_hold fails

> A use-after-free vulnerability in the Linux kernel TLS subsystem allows attackers to execute arbitrary code or escalate privileges via async decryption failures.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 12 Nov 2025
- **Updated:** 15 Oct 2026
- **Also known as:** AZL-70028, BELL-CVE-2025-40176, DEBIAN-CVE-2025-40176, GHSA-79rw-jwgh-qv55, ROOT-OS-DEBIAN-13-CVE-2025-40176, ROOT-OS-UBUNTU-2404-CVE-2025-40176, UBUNTU-CVE-2025-40176

## What is CVE-2025-40176?

CVE-2025-40176 is a critical use after free vulnerability in Linux, published on 12 Nov 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

tls: wait for pending async decryptions if tls_strp_msg_hold fails

Async decryption calls tls_strp_msg_hold to create a clone of the
input skb to hold references to the memory it uses. If we fail to
allocate that clone, proceeding with async decryption can lead to
various issues (UAF on the skb, writing into userspace memory after
the recv() call has returned).

In this case, wait for all pending decryption requests.

## Which versions are affected by CVE-2025-40176?


## How do I fix CVE-2025-40176?

Apply the vendor's patch.

## Is CVE-2025-40176 being exploited?

There is no known exploitation of CVE-2025-40176 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40176 and fix it if it is affected.

What it is: CVE-2025-40176 is a critical use after free vulnerability in Linux, published on 12 Nov 2025. 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-2025-40176 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2025-40176/ (Markdown: https://insights.sbomify.com/CVE-2025-40176/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40176
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40176
- OSV: https://osv.dev/vulnerability/CVE-2025-40176

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40176/
Summaries are generated and may contain mistakes; the official description above is the record.