Bug 2457838 (CVE-2026-31420)

Summary: CVE-2026-31420 kernel: bridge: mrp: reject zero test interval to avoid OOM panic
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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OS: Linux   
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A flaw was found in the Linux kernel's bridge subsystem, specifically within the Multiple Registration Protocol (MRP) implementation. A local user can exploit this vulnerability by supplying a zero-value test interval through the netlink interface without proper validation. This invalid input causes a delayed work process to repeatedly reschedule itself with no delay, leading to a rapid allocation and transmission of MRP test frames. Consequently, this exhausts all available system memory, resulting in an Out-Of-Memory (OOM) deadlock and a kernel panic, effectively causing a Denial of Service (DoS).
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Description OSIDB Bzimport 2026-04-13 14:02:24 UTC 
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.
Comment 1 Keith Grant 2026-04-13 16:59:39 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026041355-CVE-2026-31420-f7b0@gregkh/T