CVE-2025-39894Network attack vector

Host panic via stale conntrack warning

Published Oct 1, 2025 · Updated Aug 5, 2026

Denial of service in affected Linux kernel releases allows remote attackers to panic hosts via broadcast traffic delivered to a bridge. After confirm() resolves a conntrack hash clash and replaces skb->_nfct, br_nf_local_in() incorrectly reads the stale nfct local and reaches WARN_ON_ONCE. Exploitation requires br_netfilter, conntrack, and bridge processing; the warning becomes a host panic when panic_on_warn is enabled.

CVSS severity7.5
High
EPSS probability0.32%
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 affected Linux kernel releases allows remote attackers to panic hosts via broadcast traffic delivered to a bridge. After confirm() resolves a conntrack hash clash and replaces skb->_nfct, br_nf_local_in() incorrectly reads the stale nfct local and reaches WARN_ON_ONCE. Exploitation requires br_netfilter, conntrack, and bridge processing; the warning becomes a host panic when panic_on_warn is enabled.

The record

CVE
CVE-2025-39894
Published
Oct 1, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 1, 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

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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=2b1414d5e94e477edff1d2c79030f1d742625ea0 <ccbad4803225eafe0175d3cb19f0d8d73b504a94
  2. Affected versionversion=5.15.151 <5.15.192
  3. Affected versionversion=6.1.81 <6.1.151
  4. Affected versionversion=62e7151ae3eb465e0ab52a20c941ff33bb6332e9 <479a54ab92087318514c82428a87af2d7af1a576
  5. Affected versionversion=62e7151ae3eb465e0ab52a20c941ff33bb6332e9 <a74abcf0f09f59daeecf7a3ba9c1d690808b0afe
  6. Affected versionversion=62e7151ae3eb465e0ab52a20c941ff33bb6332e9 <c47ca77fee9071aa543bae592dd2a384f895c8b6
  7. Affected versionversion=6.6.21 <6.6.105
  8. Affected versionversion=6.7.9 <6.8
  9. Affected versionversion=6.8
  10. Affected versionversion=7c3f28599652acf431a2211168de4a583f30b6d5 <d00c8b0daf56012f69075e3377da67878c775e4c
  11. Affected versionversion=80cd0487f630b5382734997c3e5e3003a77db315 <50db11e2bbb635e38e3dd096215580d6adb41fb0
  12. Affected versionversion=cb734975b0ffa688ff6cc0eed463865bf07b6c01

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=2b1414d5e94e477edff1d2c79030f1d742625ea0 <ccbad4803225eafe0175d3cb19f0d8d73b504a94; version=5.15.151 <5.15.192; version=6.1.81 <6.1.151; version=62e7151ae3eb465e0ab52a20c941ff33bb6332e9 <479a54ab92087318514c82428a87af2d7af1a576; version=62e7151ae3eb465e0ab52a20c941ff33bb6332e9 <a74abcf0f09f59daeecf7a3ba9c1d690808b0afe; version=62e7151ae3eb465e0ab52a20c941ff33bb6332e9 <c47ca77fee9071aa543bae592dd2a384f895c8b6; version=6.6.21 <6.6.105; version=6.7.9 <6.8; version=6.8; version=7c3f28599652acf431a2211168de4a583f30b6d5 <d00c8b0daf56012f69075e3377da67878c775e4c; version=80cd0487f630b5382734997c3e5e3003a77db315 <50db11e2bbb635e38e3dd096215580d6adb41fb0; version=cb734975b0ffa688ff6cc0eed463865bf07b6c01

Published CVSS scores

7.5Linux kernel CVE teamCVSS:3.1/AV:N/AC:L/PR:N/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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499.004Application or System Exploitation

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

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Your stack

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