CVE-2026-53043
CriticalCVSS 9.1Exploitation Probability (EPSS)
Low risk40th percentile — higher than 40% of all known CVEs
Summary
In the Linux kernel's OCFS2/DLM filesystem, a vulnerability was found due to missing validation of the qr_numregions field in dlm_match_regions(). A crafted DLM_QUERY_REGION network message can set this value above the allowed maximum (32), causing out-of-bounds reads of the qr_regions buffer. Additionally, an off-by-one error in the comparison loop was fixed.
Risk Assessment
An attacker can send a crafted network message, causing out-of-bounds memory reads in kernel space, potentially leading to information disclosure or system instability.
Recommendation
Immediately update the Linux kernel to a version containing the fix (commit from the ocfs2/dlm patch series). Before updating, restrict network access to OCFS2/DLM services.
Original NVD description (English source)
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.