CVE-2025-21805Network attack vector

Unauthenticated kernel takeover via stale IB event handler

Published Feb 27, 2025 · Updated Aug 5, 2026

Use-after-free in Linux 6.12 through 6.12.12 and 6.13 through 6.13.1 allows remote attackers to execute code via RTRS reconnects. The final RTRS path teardown frees rtrs_ib_dev without calling its deinit callback, leaving its IB event handler linked for later list writes and function-pointer dispatch. An unauthenticated peer that can reach an RNBD server over RDMA can repeatedly connect and disconnect, enabling kernel memory disclosure, kernel control-flow hijack, or a crash.

CVSS severity9.8
Critical
EPSS probability0.38%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in Linux 6.12 through 6.12.12 and 6.13 through 6.13.1 allows remote attackers to execute code via RTRS reconnects. The final RTRS path teardown frees rtrs_ib_dev without calling its deinit callback, leaving its IB event handler linked for later list writes and function-pointer dispatch. An unauthenticated peer that can reach an RNBD server over RDMA can repeatedly connect and disconnect, enabling kernel memory disclosure, kernel control-flow hijack, or a crash.

The record

CVE
CVE-2025-21805
Published
Feb 27, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 27, 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=6.12
  2. Affected versionversion=667db86bcbe82e789d82c2e8c8c40756ec2e1999 <1af2c769032b6b334cd2a867d7d8c7cbbc527b2d
  3. Affected versionversion=667db86bcbe82e789d82c2e8c8c40756ec2e1999 <5a79cc9bc961fafe90787f86e8f53ba6fad8d63b
  4. Affected versionversion=667db86bcbe82e789d82c2e8c8c40756ec2e1999 <81468c4058a62e84e475433b83b3edc613294f5e

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=6.12; version=667db86bcbe82e789d82c2e8c8c40756ec2e1999 <1af2c769032b6b334cd2a867d7d8c7cbbc527b2d; version=667db86bcbe82e789d82c2e8c8c40756ec2e1999 <5a79cc9bc961fafe90787f86e8f53ba6fad8d63b; version=667db86bcbe82e789d82c2e8c8c40756ec2e1999 <81468c4058a62e84e475433b83b3edc613294f5e

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
9.8Linux Kernel CNACVSS: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 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

T1190Exploit Public-Facing Application

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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