Junglewise Threat Intelligence

CVE-2026-43065: Linux Kernel ext4 resource leak in ext4_mb_release

CVE-2026-43065 · Severity: medium · CVSS 5.5 · Published 2026-05-05

Technologies: Linux Kernel. Vendors: Linux.

Executive brief

A vulnerability was identified in the Linux kernel's ext4 filesystem component. Under specific conditions involving changing filesystem mount options and unmounting, the system may fail to properly clean up background tasks responsible for freeing disk space. This could potentially lead to system instability or a denial-of-service condition where the system crashes or hangs during shutdown.

Technical details

A race condition and resource management bug exists in the ext4 multiblock allocator (mballoc.c). When a filesystem is mounted with the 'discard' option, file deletions populate 's_discard_list' and queue 's_discard_work'. If the filesystem is subsequently remounted with 'nodiscard', the EXT4_MOUNT_DISCARD flag is cleared, causing 'ext4_mb_release()' to skip flushing the work queue. This results in pending work remaining active or uncleaned during unmount. An attacker with local access could potentially trigger this by manipulating mount options and performing large-scale deletions to cause a kernel panic or memory corruption. The fix ensures 'flush_work' is always called in 'ext4_mb_release()' regardless of the current mount flags.

Affected products

  • Linux Linux Kernel 5.15 to 5.15.203, 5.16 to 6.1.168, 6.2 to 6.6.131, 6.7 to 6.12.80, 6.13 to 6.18.21, 6.19 to 6.19.11, 7.0-rc1 to 7.0-rc5

Timeline

  • 2026-03-27: patched: Initial patch authored by Theodore Ts'o
  • 2026-05-05: advisory: CVE-2026-43065 published

References

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