# CVE-2026-31420

## Summary

- **CVE ID:** CVE-2026-31420
- **Severity:** MEDIUM
- **CVSS Score:** 5.5 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H)
- **CWE:** N/A
- **Published:** Apr 13, 2026
- **Last Modified:** Sep 14, 2026

## 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.

## Affected Products

- Linux — Linux (20f6a05ef63594feb0c6dfbd629da0448b43124d)
- Linux — Linux (5.8)
- Linux — Linux (0)
- Linux — Linux (6.19.12)
- Linux — Linux (7.0)
- Linux — Linux (6.12.92)
- Linux — Linux (6.18.34)
- Linux — Linux (5.10.270)
- Linux — Linux (5.15.221)
- Linux — Linux (6.1.188)
- Linux — Linux (6.6.157)

## References

- [CNA](https://git.kernel.org/stable/c/c9bc352f716d1bebfe43354bce539ec2d0223b30)
- [CNA](https://git.kernel.org/stable/c/fa6e24963342de4370e3a3c9af41e38277b74cf3)
- [CNA](https://git.kernel.org/stable/c/630a15a31c2034b5b697f4aabc769b9d80d82446)
- [CNA](https://git.kernel.org/stable/c/e8ec80430bfa520e7352155d6ac632e527cba7aa)
- [CNA](https://git.kernel.org/stable/c/610073ffb77ffd2b5eca182d2ac264de4834a175)
- [CNA](https://git.kernel.org/stable/c/ec8850be9b2b3beac1c7967d95f169dd2785979d)
- [CNA](https://git.kernel.org/stable/c/1ec86b4b9e28170a2565cf36f0e6e2b96b55134d)
- [CNA](https://git.kernel.org/stable/c/2120bd8546cd6a63c558d135773aa8f41c8259fc)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.09%
- **EPSS Percentile:** 0.6

---
_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-18._