CVE-2026-53043 ocfs2/dlm: validate qr_numregions in dlm_match_regions()
A missing bounds check in the Linux kernel OCFS2 DLM allows out-of-bounds reads via crafted network messages, potentially causing crashes or data leaks.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-53043?
CVE-2026-53043 is a critical memory corruption vulnerability in Linux kernel, published on 24 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
ocfs2/dlm: validate qr_numregions in dlm_match_regions()
Patch series "ocfs2/dlm: fix two bugs in dlm_match_regions()".
In dlm_match_regions(), the qr_numregions field from a DLM_QUERY_REGION network message is used to drive loops over the qr_regions buffer without sufficient validation. This series fixes two issues:
- Patch 1 adds a bounds check to reject messages where qr_numregions exceeds O2NM_MAX_REGIONS. The o2net layer only validates message byte length; it does not constrain field values, so a crafted message can set qr_numregions up to 255 and trigger out-of-bounds reads past the 1024-byte qr_regions buffer.
- Patch 2 fixes an off-by-one in the local-vs-remote comparison loop, which uses '<=' instead of '<', reading one entry past the valid range even when qr_numregions is within bounds.
This patch (of 2):
The qr_numregions field from a DLM_QUERY_REGION network message is used directly as loop bounds in dlm_match_regions() without checking against O2NM_MAX_REGIONS. Since qr_regions is sized for at most O2NM_MAX_REGIONS (32) entries, a crafted message with qr_numregions > 32 causes out-of-bounds reads past the qr_regions buffer.
Add a bounds check for qr_numregions before entering the loops.
Weakness: CWE-787
Which versions are affected by CVE-2026-53043?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-53043?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-53043 being exploited?
There is no known exploitation of CVE-2026-53043 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-53043, DEBIAN-CVE-2026-53043, GHSA-hv9w-qqh8-9pfh, ROOT-OS-DEBIAN-11-CVE-2026-53043, ROOT-OS-DEBIAN-12-CVE-2026-53043, ROOT-OS-UBUNTU-2204-CVE-2026-53043 and 2 more.