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PatchSiren cyber security CVE debrief

CVE-2026-46095 Linux CVE debrief

A race condition vulnerability in the Linux kernel's MD (Multiple Device) driver bitmap subsystem has been resolved. The issue existed in the md-llbitmap module, where barrier operations were incorrectly ordered relative to state machine transitions in the `llbitmap_start_write()` and `llbitmap_start_discard()` functions. The vulnerability could allow the state machine to complete before the barrier was properly raised, potentially leading to data corruption or inconsistent bitmap states during RAID array operations. The fix repositions the barrier raise operation to occur before calling `llbitmap_state_machine()`, ensuring proper synchronization. This affects Linux kernel stable branches and has been addressed with commits to the kernel source tree.

Vendor
Linux
Product
Unknown
CVSS
Unknown
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-27
Original CVE updated
2026-05-27
Advisory published
2026-05-27
Advisory updated
2026-05-27

Who should care

System administrators managing Linux servers with MD RAID arrays, particularly those utilizing bitmap functionality for resync optimization; kernel maintainers and distribution security teams responsible for stable kernel backports; organizations running software-defined storage or high-availability clusters dependent on Linux MD RAID

Technical summary

The vulnerability resided in `drivers/md/md-llbitmap.c` where memory barrier operations were sequenced after state machine entry points. In `llbitmap_start_write()` and `llbitmap_start_discard()`, the barrier raise occurred following the `llbitmap_state_machine()` call, creating a window where concurrent operations could observe inconsistent state. The correction moves `raise_barrier()` invocations to precede state machine transitions, establishing proper happens-before relationships for bitmap state changes. This is a classic compiler/architecture memory ordering bug with potential impact on RAID resync and recovery operations.

Defensive priority

medium

Recommended defensive actions

  • Apply kernel updates containing the referenced stable branch commits when available through your Linux distribution's security channel
  • Verify running kernel version against patched versions in stable branches
  • Monitor RAID array health and bitmap consistency if running unpatched kernels with MD RAID configurations
  • Review system logs for any bitmap-related errors or inconsistencies
  • Schedule maintenance windows for kernel updates on systems utilizing MD RAID with bitmap functionality

Evidence notes

The CVE description confirms this is a resolved Linux kernel vulnerability in the md/md-llbitmap subsystem. The fix involves moving barrier raise operations before state machine transitions in `llbitmap_start_write()` and `llbitmap_start_discard()` functions. Three kernel.org stable branch commits are referenced, indicating backports to maintained kernel versions. The NVD entry shows status 'Awaiting Analysis' with no CVSS score assigned. No KEV listing or known ransomware campaign use is indicated.

Official resources

2026-05-27