Linux Kernel up to 7.1.7 EROFS/fscache comparison

Summaryinfo

A vulnerability, which was classified as very critical, was found in Linux Kernel up to 7.1.7. This impacts an unknown function of the component EROFS/fscache. Executing a manipulation can lead to comparison. This vulnerability is registered as CVE-2026-80899. It is possible to launch the attack remotely. No exploit is available.

Detailsinfo

A vulnerability has been found in Linux Kernel up to 7.1.7 and classified as very critical. This vulnerability affects some unknown functionality of the component EROFS/fscache. The manipulation with an unknown input leads to a comparison vulnerability. The CWE definition for the vulnerability is CWE-697. The product compares two entities in a security-relevant context, but the comparison is incorrect, which may lead to resultant weaknesses. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: erofs: remove fscache backend entirely EROFS over fscache was introduced to provide image lazy pulling functionality. After the feature landed, the fscache subsystem made netfs a new hard dependency, which is unexpected for a local filesystem and has an kernel-defined caching hierarchy which could be inflexible compared to the fanotify pre-content hooks. Therefore, this feature has been deprecated for almost two years. As EROFS file-backed mounts and fanotify pre-content hooks both upstream for a while and already providing equivalent functionality (erofs-utils has supported fanotify pre-content hooks), let's remove the fscache backend now. The main application of this feature is Nydus [1], and they plan to move to use fanotify pre-content hooks in the near future too. I hope this patch can be merged into Linux 7.2, which is also motivated by newly found implementation issues [2][3] that are not worth investigating given the deprecation and limited development resources. The associated fscache/cachefiles cleanup patch will follow separately through the vfs tree (netfs) later: it seems fine since the codebase is isolated by CONFIG_CACHEFILES_ONDEMAND. [1] https://github.com/dragonflyoss/nydus/blob/v2.1.0/docs/nydus-fscache.md [2] https://github.com/dragonflyoss/nydus/pull/1824 [3] https://lore.kernel.org/r/[email protected]

The advisory is shared for download at git.kernel.org. This vulnerability was named CVE-2026-80899 since 08/26/2026. The exploitation appears to be easy. The attack can be initiated remotely. There are neither technical details nor an exploit publicly available. The current price for an exploit might be approx. USD $5k-$25k (estimation calculated on 09/04/2026).

Upgrading to version 7.1.8 eliminates this vulnerability. Applying the patch f6145794f17a27d25f8a84edb80731fb0e07c196/c37460cd9b2fcb61ec66b7eb4fde737e65ec2a56 is able to eliminate this problem.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 7.1.0
• 7.1.1
• 7.1.2
• 7.1.3
• 7.1.4
• 7.1.5
• 7.1.6
• 7.1.7

License

• open-source

Website

• Vendor: https://www.kernel.org/

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