# CVE-2025-39802: linux: In the Linux kernel, the following vulnerability has been resolved:  lib/crypto: arm/poly1305: Fix register corruptio...

CVE-2025-39802 is fixed in linux on 1 platform by DEBIAN-CVE-2025-39802 (version 6.16.5-1), released September 15, 2025. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2025-39802
- Priority: High
- CVSS: 7.8 (high)
- EPSS: 0.0025
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 15, 2025

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 14 | 6.16.5-1 | [DEBIAN-CVE-2025-39802](https://patchblox.com/security/data/fix/linux/debian-cve-2025-39802.md) | Sep 15, 2025 |

---

Data as of 2026-11-08T06:59:42Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

Free to use with attribution: show "Data: Patchblox Patch Radar" with a link to https://patchblox.com/security/patch-radar. Terms, including what needs a written agreement: https://patchblox.com/security/patch-radar/use-the-data

Product names, logos and trademarks shown on Patch Radar belong to their respective owners. They are used only to identify the software each security fix applies to and to help readers find their platform. Their use does not imply any affiliation with, or endorsement by, those owners, and Patchblox is not affiliated with any of them.