CVE-2025-39804

Task-state corruption via unchecked SIMD use

Published Sep 15, 2025 · Updated Aug 5, 2026

Register corruption in Linux 6.16 on arm64 allows local users to alter task state or produce incorrect Poly1305 MACs in no-SIMD contexts. The arm64 Poly1305 glue code calls SIMD-backed functions without checking may_use_simd(), so calls made while SIMD registers are unavailable can overwrite unrelated tasks' registers or return a wrong authenticator. Reachability requires local low-privileged execution on arm64 and a kernel path that invokes Poly1305 while SIMD use is prohibited; the documented consequences are register corruption and incorrect MAC computation.

CVSS severity7.8
High
EPSS probability0.25%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Register corruption in Linux 6.16 on arm64 allows local users to alter task state or produce incorrect Poly1305 MACs in no-SIMD contexts. The arm64 Poly1305 glue code calls SIMD-backed functions without checking may_use_simd(), so calls made while SIMD registers are unavailable can overwrite unrelated tasks' registers or return a wrong authenticator. Reachability requires local low-privileged execution on arm64 and a kernel path that invokes Poly1305 while SIMD use is prohibited; the documented consequences are register corruption and incorrect MAC computation.

The record

CVE
CVE-2025-39804
Published
Sep 15, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
Unavailable
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 15, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=6.16
  2. Affected versionversion=a59e5468a921937cb7317892779c67046ad9f5cc <eec76ea5a7213c48529a46eed1b343e5cee3aaab
  3. Affected versionversion=a59e5468a921937cb7317892779c67046ad9f5cc <ef74efa598b7bbc5c24509f7f56af2806f81c339

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=6.16; version=a59e5468a921937cb7317892779c67046ad9f5cc <eec76ea5a7213c48529a46eed1b343e5cee3aaab; version=a59e5468a921937cb7317892779c67046ad9f5cc <ef74efa598b7bbc5c24509f7f56af2806f81c339

Published CVSS scores

7.8NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

No sourced classifications are available.

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo