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CVE-2025-39802

7.5 · HIGH

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 comm…

Published Sep 15, 2025EPSS 0.25%

Overview

CVE-2025-39802 is a high-severity vulnerability. It was published on September 15, 2025 and has a CVSS 3.1 base score of 7.5 (HIGH).

This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refgit.kernel.org/stable/c/52c3e242f4d0043186b70d65460ba1767f27494aRefgit.kernel.org/stable/c/87bdfba903be7084cb3ee04032b14a81181fe413

How CyberStrike helps

Frequently asked questions

What is CVE-2025-39802?

CVE-2025-39802 is a high-severity vulnerability. It was published on September 15, 2025 and has a CVSS 3.1 base score of 7.5 (HIGH).

How severe is CVE-2025-39802?

This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2025-39802?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2025-39802?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2025-39802 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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