CVE-2025-21791

Local privilege escalation via VRF teardown race

Published Feb 27, 2025 · Updated Aug 5, 2026

Use-after-free in the Linux kernel VRF path allows local users to gain kernel privileges through concurrent VRF teardown and packet sends. The l3mdev_l3_out function dereferences VRF master adjacency data without an RCU read-side critical section while another thread can free it. A local unprivileged user can obtain CAP_NET_ADMIN in a user namespace, race packet transmission against VRF unenslave or deletion, and trigger a kernel crash or control-flow hijack.

CVSS severity7.8
High
EPSS probability0.26%
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 the Linux kernel VRF path allows local users to gain kernel privileges through concurrent VRF teardown and packet sends. The l3mdev_l3_out function dereferences VRF master adjacency data without an RCU read-side critical section while another thread can free it. A local unprivileged user can obtain CAP_NET_ADMIN in a user namespace, race packet transmission against VRF unenslave or deletion, and trigger a kernel crash or control-flow hijack.

The record

CVE
CVE-2025-21791
Published
Feb 27, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-416, T1068
Attack vector
local
Privileges
authenticated

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

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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=4.9
  2. Affected versionversion=a8e3e1a9f02094145580ea7920c6a1d9aabd5539 <022cac1c693add610ae76ede03adf4d9d5a2cf21
  3. Affected versionversion=a8e3e1a9f02094145580ea7920c6a1d9aabd5539 <20a3489b396764cc9376e32a9172bee26a89dc3b
  4. Affected versionversion=a8e3e1a9f02094145580ea7920c6a1d9aabd5539 <5bb4228c32261d06e4fbece37ec3828bcc005b6b
  5. Affected versionversion=a8e3e1a9f02094145580ea7920c6a1d9aabd5539 <6ccaa5797f5362a2aad6baa6ddaf4715ac2dd51e
  6. Affected versionversion=a8e3e1a9f02094145580ea7920c6a1d9aabd5539 <6d0ce46a93135d96b7fa075a94a88fe0da8e8773
  7. Affected versionversion=a8e3e1a9f02094145580ea7920c6a1d9aabd5539 <7b81425b517accefd46bee854d94954f5c57e019
  8. Affected versionversion=a8e3e1a9f02094145580ea7920c6a1d9aabd5539 <c40cb5c03e37552d6eff963187109e2c3f78ef6f
  9. Affected versionversion=a8e3e1a9f02094145580ea7920c6a1d9aabd5539 <c7574740be8ce68a57d0aece24987b9be2114c3c

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=4.9; version=a8e3e1a9f02094145580ea7920c6a1d9aabd5539 <022cac1c693add610ae76ede03adf4d9d5a2cf21; version=a8e3e1a9f02094145580ea7920c6a1d9aabd5539 <20a3489b396764cc9376e32a9172bee26a89dc3b; version=a8e3e1a9f02094145580ea7920c6a1d9aabd5539 <5bb4228c32261d06e4fbece37ec3828bcc005b6b; version=a8e3e1a9f02094145580ea7920c6a1d9aabd5539 <6ccaa5797f5362a2aad6baa6ddaf4715ac2dd51e; version=a8e3e1a9f02094145580ea7920c6a1d9aabd5539 <6d0ce46a93135d96b7fa075a94a88fe0da8e8773; version=a8e3e1a9f02094145580ea7920c6a1d9aabd5539 <7b81425b517accefd46bee854d94954f5c57e019; version=a8e3e1a9f02094145580ea7920c6a1d9aabd5539 <c40cb5c03e37552d6eff963187109e2c3f78ef6f; version=a8e3e1a9f02094145580ea7920c6a1d9aabd5539 <c7574740be8ce68a57d0aece24987b9be2114c3c

Published CVSS scores

7.8LinuxCVSS: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.

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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)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-416Use After Free
T1068Exploitation for Privilege Escalation

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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