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

CVE-2026-31420 is fixed in 11 products on 1 platform, first by DEBIAN-CVE-2026-31420, released April 13, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-31420
- Priority: Routine
- CVSS: 5.5 (Moderate)
- EPSS: 0.0009
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Apr 13, 2026
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-31420

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | kernel-64kb sles 15.7 | 6.4.0-150700.53.55.1 | [SUSE-SU-2026:2238-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-2238-1.md) | Jun 30, 2026 |
| Linux | kernel-azure sles 15.7 | 6.4.0-150700.53.55.1 | [SUSE-SU-2026:2238-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-2238-1.md) | Jun 30, 2026 |
| Linux | kernel-default sles 15.7 | 6.4.0-150700.53.55.1 | [SUSE-SU-2026:2238-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-2238-1.md) | Jun 30, 2026 |
| Linux | kernel-default-base sles 15.7 | 6.4.0-150700.53.55.1.150700.17.33.1 | [SUSE-SU-2026:2238-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-2238-1.md) | Jun 30, 2026 |
| Linux | kernel-docs sles 15.7 | 6.4.0-150700.53.55.1 | [SUSE-SU-2026:2238-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-2238-1.md) | Jun 30, 2026 |
| Linux | kernel-livepatch-SLE15-SP7_Update_15 sles 15.7 | 1-150700.15.3.1 | [SUSE-SU-2026:2238-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-2238-1.md) | Jun 30, 2026 |
| Linux | kernel-obs-build sles 15.7 | 6.4.0-150700.53.55.1 | [SUSE-SU-2026:2238-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-2238-1.md) | Jun 30, 2026 |
| Linux | kernel-source sles 15.7 | 6.4.0-150700.53.55.1 | [SUSE-SU-2026:2238-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-2238-1.md) | Jun 30, 2026 |
| Linux | kernel-syms sles 15.7 | 6.4.0-150700.53.55.1 | [SUSE-SU-2026:2238-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-2238-1.md) | Jun 30, 2026 |
| Linux | kernel-zfcpdump sles 15.7 | 6.4.0-150700.53.55.1 | [SUSE-SU-2026:2238-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-2238-1.md) | Jun 30, 2026 |
| Linux | linux Debian 12.15 (bookworm) | 6.1.190-1 | [DEBIAN-CVE-2026-31420](https://patchblox.com/security/data/fix/linux/debian-cve-2026-31420.md) | Apr 13, 2026 |
| Linux | linux Debian 13.5 (trixie) | 6.12.94-1 | [DEBIAN-CVE-2026-31420](https://patchblox.com/security/data/fix/linux/debian-cve-2026-31420.md) | Apr 13, 2026 |
| Linux | linux Debian 14 | 6.19.12-1 | [DEBIAN-CVE-2026-31420](https://patchblox.com/security/data/fix/linux/debian-cve-2026-31420.md) | Apr 13, 2026 |

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Data as of 2026-11-08T19:12:23Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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