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CVE-2025-21691 is an incorrect-authorization vulnerability in the Linux kernel's cachestat() system call. cachestat() was introduced as a file-based alternative to mincore() for obtaining page-cache statistics, but did not implement the conservative ownership-or-writability validation previously added to mincore(). Consequently, a local caller could request page-cache statistics for files without satisfying the intended ownership or write-access condition. The fix adds equivalent permission-checking logic to cachestat(), adapted to its file-context implementation.
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No public exploit code observed for this vulnerability.
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Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
7 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A Linux kernel cachestat vulnerability involving page cache statistics permission checking, fixed in this Red Hat kernel update.
A Linux kernel vulnerability related to page cache attack techniques; the content indicates it has been remediated by the Linux kernel security team.
Linux kernel cachestat permission-checking vulnerability.
Linux kernel authorization flaw in the cachestat() system call where permission checking was insufficient, potentially allowing unauthorized access to page cache statistics/data (incorrect authorization).
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.