Linux Kernel up to 6.18.35/7.0.12 xsk xsk_skb_metadata toctou

Summaryinfo

A vulnerability classified as critical has been found in Linux Kernel up to 6.18.35/7.0.12. This affects the function xsk_skb_metadata of the component xsk. The manipulation leads to toctou. This vulnerability is traded as CVE-2026-53250. An attack has to be approached locally. There is no exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as critical, has been found in Linux Kernel up to 6.18.35/7.0.12. This issue affects the function xsk_skb_metadata of the component xsk. The manipulation with an unknown input leads to a toctou vulnerability. Using CWE to declare the problem leads to CWE-367. The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check. This can cause the product to perform invalid actions when the resource is in an unexpected state. The impact remains unknown. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: xsk: cache csum_start/csum_offset to fix TOCTOU in xsk_skb_metadata() The TX metadata area resides in the UMEM buffer which is memory-mapped and concurrently writable by userspace. In xsk_skb_metadata(), csum_start and csum_offset are read from shared memory for bounds validation, then read again for skb assignment. A malicious userspace application can race to overwrite these values between the two reads, bypassing the bounds check and causing out-of-bounds memory access during checksum computation in the transmit path. Fix this by reading csum_start and csum_offset into local variables once, then using the local copies for both validation and assignment. Note that other metadata fields (flags, launch_time) and the cached csum fields may be mutually inconsistent due to concurrent userspace writes, but this is benign: the only security-critical invariant is that each field's validated value is the same one used, which local caching guarantees.

It is possible to read the advisory at git.kernel.org. The identification of this vulnerability is CVE-2026-53250 since 06/09/2026. The exploitation is known to be difficult. Attacking locally is a requirement. Technical details of the vulnerability are known, but there is no available exploit.

Upgrading to version 6.18.36 or 7.0.13 eliminates this vulnerability. Applying the patch 0dfe05b938435892875e07771170051346412df9/bfdfd2706d5fb2cd496a1506e680daf979309c8b/22ba97ea9cc1f63a0d0244fae38057ed452b6ac7 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. 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

• 6.18.0
• 6.18.1
• 6.18.2
• 6.18.3
• 6.18.4
• 6.18.5
• 6.18.6
• 6.18.7
• 6.18.8
• 6.18.9
• 6.18.10
• 6.18.11
• 6.18.12
• 6.18.13
• 6.18.14
• 6.18.15
• 6.18.16
• 6.18.17
• 6.18.18
• 6.18.19
• 6.18.20
• 6.18.21
• 6.18.22
• 6.18.23
• 6.18.24
• 6.18.25
• 6.18.26
• 6.18.27
• 6.18.28
• 6.18.29
• 6.18.30
• 6.18.31
• 6.18.32
• 6.18.33
• 6.18.34
• 6.18.35
• 7.0.0
• 7.0.1
• 7.0.2
• 7.0.3
• 7.0.4
• 7.0.5
• 7.0.6
• 7.0.7
• 7.0.8
• 7.0.9
• 7.0.10
• 7.0.11
• 7.0.12

License

• open-source

Website

• Vendor: https://www.kernel.org/

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