Linux Kernel up to 7.2.5 dm-pcache cache_pos_decode out-of-bounds

Summaryinfo

A vulnerability categorized as very critical has been discovered in Linux Kernel up to 7.2.5. The impacted element is the function cache_pos_decode of the component dm-pcache. Such manipulation leads to out-of-bounds. This vulnerability is uniquely identified as CVE-2026-93201. Local access is required to approach this attack. No exploit exists. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 7.2.5 and classified as very critical. Affected by this issue is the function cache_pos_decode of the component dm-pcache. The manipulation with an unknown input leads to a out-of-bounds vulnerability. Using CWE to declare the problem leads to CWE-125. The product reads data past the end, or before the beginning, of the intended buffer. Impacted is confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: dm-pcache: validate seg_id fields from persistent memory cache_pos_decode(), cache_key_decode() and the last-kset branches of cache_replay(), the writeback worker and the GC worker take a cache segment id from the cache device metadata and index cache->segments[] with it without checking it against cache->n_segs. That metadata is only CRC-protected with a fixed public seed, so whoever supplies the cache device on a table load (CAP_SYS_ADMIN) controls the id; an out-of-range value forms a wild pcache_cache_segment pointer that is dereferenced and written through -- an out-of-bounds read and write driven by on-disk data. Add cache_seg_id_valid() and reject an out-of-range id at each decode site, failing the operation with -EIO instead of indexing past the array. Bound the id against the initialized-segment count (cache_info.n_segs) rather than the physical device total. A forged cache_info.n_segs below seg_num otherwise leaves segments[cache_info.n_segs..seg_num) as zeroed structs whose data pointer is NULL, so a forged id in that window would still be dereferenced. A later patch guarantees cache_info.n_segs <= seg_num, and a driver-created cache sets the two equal, so valid images are unaffected.

The advisory is available at git.kernel.org. This vulnerability is handled as CVE-2026-93201 since 09/17/2026. The exploitation is known to be easy. Local access is required to approach this attack. Additional levels of successful authentication are required for exploitation. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 09/18/2026).

Upgrading to version 7.2.6 or 7.3-rc1 eliminates this vulnerability. Applying the patch b4bf8af5e7d7db4c5e179e15017da55857761ac4/90c990a68460d7b5720e5634cf650eccdf0f4098 is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 7.2.0
• 7.2.1
• 7.2.2
• 7.2.3
• 7.2.4
• 7.2.5

License

• open-source

Website

• Vendor: https://www.kernel.org/

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