# CVE-2026-52993: tipc: fix double-free in tipc_buf_append()

> A double-free vulnerability in the Linux kernel's TIPC module allows attackers to potentially execute arbitrary code or escalate privileges.

- **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:** 24 Jun 2026
- **Updated:** 19 Oct 2026
- **Also known as:** A-500022799, ASB-A-500022799, BELL-CVE-2026-52993, DEBIAN-CVE-2026-52993, GHSA-m86q-cgj9-94c8, ROOT-OS-DEBIAN-11-CVE-2026-52993, ROOT-OS-DEBIAN-12-CVE-2026-52993, ROOT-OS-UBUNTU-2204-CVE-2026-52993, ROOT-OS-UBUNTU-2404-CVE-2026-52993, UBUNTU-CVE-2026-52993

## What is CVE-2026-52993?

CVE-2026-52993 is a critical use after free vulnerability in Linux kernel, published on 24 Jun 2026. 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:

tipc: fix double-free in tipc_buf_append()

tipc_msg_validate() can potentially reallocate the skb it is validating,
freeing the old one.  In tipc_buf_append(), it was being called with a
pointer to a local variable which was a copy of the caller's skb
pointer.

If the skb was reallocated and validation subsequently failed, the error
handling path would free the original skb pointer, which had already
been freed, leading to double-free.

Fix this by checking if head now points to a newly allocated reassembled
skb.  If it does, reassign *headbuf for later freeing operations.

Weakness: CWE-415 (Double Free), CWE-763 (Release of Invalid Pointer or Reference)

## Which versions are affected by CVE-2026-52993?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-52993?

Apply the vendor's patch.

## Is CVE-2026-52993 being exploited?

There is no known exploitation of CVE-2026-52993 in the wild and no public exploit code.

Public exploit code:

- https://github.com/CaptainAI-Labs/CaptainAI-LPE-CVE-2026-52993 (github_poc): https://github.com/CaptainAI-Labs/CaptainAI-LPE-CVE-2026-52993

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-52993 and fix it if it is affected.

What it is: CVE-2026-52993 is a critical use after free vulnerability in Linux kernel, published on 24 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-2026-52993 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-52993/ (Markdown: https://insights.sbomify.com/CVE-2026-52993/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-52993
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-52993
- OSV: https://osv.dev/vulnerability/CVE-2026-52993

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-52993/
Summaries are generated and may contain mistakes; the official description above is the record.