Linux Kernel up to 6.16.3 lib/crypto may_use_simd memory corruption

Summaryinfo

A vulnerability was found in Linux Kernel up to 6.16.3. It has been classified as critical. This vulnerability affects the function may_use_simd in the library lib/crypto. The manipulation leads to memory corruption. This vulnerability is traded as CVE-2025-39802. There is no exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.16.3. It has been rated as critical. This issue affects the function may_use_simd in the library lib/crypto. The manipulation with an unknown input leads to a memory corruption vulnerability. Using CWE to declare the problem leads to CWE-119. The product performs operations on a memory buffer, but it can read from or write to a memory location that is outside of the intended boundary of the buffer. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: lib/crypto: arm/poly1305: Fix register corruption in no-SIMD contexts Restore the SIMD usability check that was removed by commit 773426f4771b ("crypto: arm/poly1305 - Add block-only interface"). This safety check is cheap and is well worth eliminating a footgun. While the Poly1305 functions should not be called when SIMD registers are unusable, if they are anyway, they should just do the right thing instead of corrupting random tasks' registers and/or computing incorrect MACs. Fixing this is also needed for poly1305_kunit to pass. Just use may_use_simd() instead of the original crypto_simd_usable(), since poly1305_kunit won't rely on crypto_simd_disabled_for_test.

The advisory is shared at git.kernel.org. The identification of this vulnerability is CVE-2025-39802 since 04/16/2025. The exploitation is known to be easy. Technical details are known, but no exploit is available. The price for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 01/11/2026).

Upgrading to version 6.16.4 or 6.17-rc1 eliminates this vulnerability. Applying the patch 87bdfba903be7084cb3ee04032b14a81181fe413/52c3e242f4d0043186b70d65460ba1767f27494a 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.

The vulnerability is also documented in the databases at EUVD (EUVD-2025-29184) and CERT Bund (WID-SEC-2025-2053). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Affected

• Debian Linux
• Amazon Linux 2
• Red Hat Enterprise Linux
• Ubuntu Linux
• SUSE Linux
• Oracle Linux
• IBM QRadar SIEM
• SUSE openSUSE
• Open Source Linux Kernel
• RESF Rocky Linux
• Dell Secure Connect Gateway
• F5 F5OS

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.16.0
• 6.16.1
• 6.16.2
• 6.16.3

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

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Entryinfo

If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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