CVE-2025-39880Network attack vector

Kernel memory corruption via inactive union access

Published Sep 23, 2025 · Updated Sep 23, 2025

Incorrect type handling in Linux kernel libceph allows remote attackers to corrupt kernel connection state through msgr2. Generic code in net/ceph/messenger.c reads auth_retry and increments connect_seq in the inactive v1 union member, which overlaps active v2 iterator and buffer pointers on 64-bit systems. A malicious Ceph peer or on-path attacker can trigger the pre-authentication fault path, causing repeated authorizer renewal, invalid memory access, or a kernel crash.

CVSS severity9.8
Critical
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

Incorrect type handling in Linux kernel libceph allows remote attackers to corrupt kernel connection state through msgr2. Generic code in net/ceph/messenger.c reads auth_retry and increments connect_seq in the inactive v1 union member, which overlaps active v2 iterator and buffer pointers on 64-bit systems. A malicious Ceph peer or on-path attacker can trigger the pre-authentication fault path, causing repeated authorizer renewal, invalid memory access, or a kernel crash.

The record

CVE
CVE-2025-39880
Published
Sep 23, 2025
Updated
Sep 23, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 23, 2025CVE publishedPublication date reported by the CVE source.
  2. Sep 23, 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=5.11
  2. Affected versionversion=cd1a677cad994021b19665ed476aea63f5d54f31 <23538cfbeed87159a5ac6c61e7a6de3d8d4486a8
  3. Affected versionversion=cd1a677cad994021b19665ed476aea63f5d54f31 <35dbbc3dbf8bccb2d77c68444f42c1e6d2d27983
  4. Affected versionversion=cd1a677cad994021b19665ed476aea63f5d54f31 <591ea9c30737663a471b2bb07b27ddde86b020d5
  5. Affected versionversion=cd1a677cad994021b19665ed476aea63f5d54f31 <6bd8b56899be0b514945f639a89ccafb8f8dfaef
  6. Affected versionversion=cd1a677cad994021b19665ed476aea63f5d54f31 <cdbc9836c7afadad68f374791738f118263c5371

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.11; version=cd1a677cad994021b19665ed476aea63f5d54f31 <23538cfbeed87159a5ac6c61e7a6de3d8d4486a8; version=cd1a677cad994021b19665ed476aea63f5d54f31 <35dbbc3dbf8bccb2d77c68444f42c1e6d2d27983; version=cd1a677cad994021b19665ed476aea63f5d54f31 <591ea9c30737663a471b2bb07b27ddde86b020d5; version=cd1a677cad994021b19665ed476aea63f5d54f31 <6bd8b56899be0b514945f639a89ccafb8f8dfaef; version=cd1a677cad994021b19665ed476aea63f5d54f31 <cdbc9836c7afadad68f374791738f118263c5371

Published CVSS scores

9.8Linux kernel CVE teamCVSS:3.1/AV:N/AC:L/PR:N/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.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
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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