CVE-2025-39777

Kernel crash via mismatched acomp free callback

Published Sep 11, 2025 · Updated Sep 11, 2025

Denial of service in Linux kernel 6.16 through 6.16.3 allows local users to crash the kernel through asynchronous compression. The acomp stream table stores kvfree through a const-qualified union member, then invokes workspace release through an incompatible void-pointer callback under CFI. A low-privileged local user must reach the affected deflate asynchronous-compression path on a kernel built with control-flow integrity; the reported consequence is a kernel crash.

CVSS severity5.5
Medium
EPSS probability0.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Linux kernel 6.16 through 6.16.3 allows local users to crash the kernel through asynchronous compression. The acomp stream table stores kvfree through a const-qualified union member, then invokes workspace release through an incompatible void-pointer callback under CFI. A low-privileged local user must reach the affected deflate asynchronous-compression path on a kernel built with control-flow integrity; the reported consequence is a kernel crash.

The record

CVE
CVE-2025-39777
Published
Sep 11, 2025
Updated
Sep 11, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 11, 2025CVE publishedPublication date reported by the CVE source.
  2. Sep 11, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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

  1. Affected versionversion=42d9f6c774790d290c175e8775ce9f1366438098 <7ec68c59461ca846aab9b7c2b39f63ac7c8a43cf
  2. Affected versionversion=42d9f6c774790d290c175e8775ce9f1366438098 <962ddc5a7a4b04c007bba0f3e7298cda13c62efd
  3. Affected versionversion=6.16

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=42d9f6c774790d290c175e8775ce9f1366438098 <7ec68c59461ca846aab9b7c2b39f63ac7c8a43cf; version=42d9f6c774790d290c175e8775ce9f1366438098 <962ddc5a7a4b04c007bba0f3e7298cda13c62efd; version=6.16

Published CVSS scores

5.5NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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