CVE-2025-21891

Service interruption via non-linear network header access

Published Mar 27, 2025 · Updated May 11, 2026

Uninitialized-resource use in the Linux kernel allows local users to interrupt service through ipvlan L3 packet transmission. ipvlan_process_v6_outbound() assumes the IPv6 header is in skb->head and reads it without first pulling non-linear data into the skb linear area. Reachability requires local packet transmission through an affected ipvlan L3 interface; the demonstrated consequence is an uninitialized-value fault.

CVSS severity5.5
Medium
EPSS probability0.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Uninitialized-resource use in the Linux kernel allows local users to interrupt service through ipvlan L3 packet transmission. ipvlan_process_v6_outbound() assumes the IPv6 header is in skb->head and reads it without first pulling non-linear data into the skb linear area. Reachability requires local packet transmission through an affected ipvlan L3 interface; the demonstrated consequence is an uninitialized-value fault.

The record

CVE
CVE-2025-21891
Published
Mar 27, 2025
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-908, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 27, 2025CVE publishedPublication date reported by the CVE source.
  2. May 11, 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=2ad7bf3638411cb547f2823df08166c13ab04269 <27843ce6ba3d3122b65066550fe33fb8839f8aef
  2. Affected versionversion=2ad7bf3638411cb547f2823df08166c13ab04269 <4ec48f812804f370f622e0874e6dd8fcc58241cd
  3. Affected versionversion=2ad7bf3638411cb547f2823df08166c13ab04269 <5353fd89663c48f56bdff975c562cfe78b1a2e4c
  4. Affected versionversion=2ad7bf3638411cb547f2823df08166c13ab04269 <5b8dea8d1612dc7151d2457d7d2e6a69820309bf
  5. Affected versionversion=2ad7bf3638411cb547f2823df08166c13ab04269 <e2a4f76a2d8a44816ecd25bcbdb47b786d621974
  6. Affected versionversion=3.19

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=2ad7bf3638411cb547f2823df08166c13ab04269 <27843ce6ba3d3122b65066550fe33fb8839f8aef; version=2ad7bf3638411cb547f2823df08166c13ab04269 <4ec48f812804f370f622e0874e6dd8fcc58241cd; version=2ad7bf3638411cb547f2823df08166c13ab04269 <5353fd89663c48f56bdff975c562cfe78b1a2e4c; version=2ad7bf3638411cb547f2823df08166c13ab04269 <5b8dea8d1612dc7151d2457d7d2e6a69820309bf; version=2ad7bf3638411cb547f2823df08166c13ab04269 <e2a4f76a2d8a44816ecd25bcbdb47b786d621974; version=3.19

Published CVSS scores

5.5CISA ADPCVSS: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 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-908Use of Uninitialized Resource
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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