CVE-2025-21868

Local service interrupt via undersized skb head cache

Published Mar 27, 2025 · Updated Aug 5, 2026

Allocation flaw in the Linux kernel allows local users to interrupt service when an affected networking build initializes. The small head cache can be smaller than GRO_MAX_HEAD when MAX_SKB_FRAGS is 45, so napi_get_frags() uses the page-fragment allocator and reaches a warning path. The affected build condition is required; systems configured to panic on warnings crash or reboot, while the default records a kernel warning.

CVSS severity5.5
Medium
EPSS probability0.37%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Allocation flaw in the Linux kernel allows local users to interrupt service when an affected networking build initializes. The small head cache can be smaller than GRO_MAX_HEAD when MAX_SKB_FRAGS is 45, so napi_get_frags() uses the page-fragment allocator and reaches a warning path. The affected build condition is required; systems configured to panic on warnings crash or reboot, while the default records a kernel warning.

The record

CVE
CVE-2025-21868
Published
Mar 27, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 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=3948b05950fdd64002a5f182c65ba5cf2d53cf71 <14ad6ed30a10afbe91b0749d6378285f4225d482
  2. Affected versionversion=3948b05950fdd64002a5f182c65ba5cf2d53cf71 <648e440c98e260dec835e48a5d7a9993477b1f9d
  3. Affected versionversion=3948b05950fdd64002a5f182c65ba5cf2d53cf71 <ed0ca7d2127c63991cfaf1932b827e3f4f8ee480
  4. Affected versionversion=3948b05950fdd64002a5f182c65ba5cf2d53cf71 <ed8a77fee4618facd2a539cad7b7366697b5a575
  5. Affected versionversion=6.4

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=3948b05950fdd64002a5f182c65ba5cf2d53cf71 <14ad6ed30a10afbe91b0749d6378285f4225d482; version=3948b05950fdd64002a5f182c65ba5cf2d53cf71 <648e440c98e260dec835e48a5d7a9993477b1f9d; version=3948b05950fdd64002a5f182c65ba5cf2d53cf71 <ed0ca7d2127c63991cfaf1932b827e3f4f8ee480; version=3948b05950fdd64002a5f182c65ba5cf2d53cf71 <ed8a77fee4618facd2a539cad7b7366697b5a575; version=6.4

Published CVSS scores

5.5GitHubCVSS: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

T1499Endpoint Denial of Service

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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