Linux Kernel up to 7.2.4 zram mark_slot_accessed race condition

Summaryinfo

A vulnerability labeled as very critical has been found in Linux Kernel up to 7.2.4. The affected element is the function mark_slot_accessed of the component zram. Such manipulation leads to race condition. This vulnerability is traded as CVE-2026-90043. An attack has to be approached locally. There is no exploit available. The affected component should be upgraded.

Detailsinfo

A vulnerability, which was classified as very critical, has been found in Linux Kernel up to 7.2.4. Affected by this issue is the function mark_slot_accessed of the component zram. The manipulation with an unknown input leads to a race condition vulnerability. Using CWE to declare the problem leads to CWE-362. The product contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently. Impacted is confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: zram: fix slot lock bit position on big-endian 64-bit The slot lock is a bit operation on the whole __lock word, which flags and ac_time alias as two u32s. On little-endian the lock bit lands in the position ZRAM_ENTRY_LOCK reserves in flags, so the aliasing works out. On 64-bit big-endian it lands in ac_time instead: with ZRAM_TRACK_ENTRY_ACTIME enabled, storing the access time from mark_slot_accessed() or slot_free() wipes out the held lock bit, letting another CPU take the same slot lock; an access time value with that bit set makes the slot look locked forever. Shift the lock bit into the flags half of the word on big-endian 64-bit.

The advisory is shared for download at git.kernel.org. This vulnerability is handled as CVE-2026-90043 since 09/11/2026. The exploitation is known to be easy. The attack needs to be approached locally. Additional levels of successful authentication are needed for exploitation. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 09/16/2026).

Upgrading to version 7.2.5 or 7.3-rc1 eliminates this vulnerability. Applying the patch 052b6b2d5fe97547bd2cdb73fa894f6cfea68b11/a8b5875741d416703e19ad8eeac6fce8a12bd6e4 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

License

• open-source

Website

• Vendor: https://www.kernel.org/

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