CVE-2025-37823

Local kernel compromise via stale HFSC class

Published May 8, 2025 · Updated Aug 5, 2026

Use-after-free in Linux 2.6.12 and later HFSC schedulers allows local users to compromise the kernel through traffic-control operations. The hfsc_dequeue() path can leave a freed hfsc_class linked in the eligible tree when a child qdisc returns no packet, then dereference the reclaimed class. A local user can obtain CAP_NET_ADMIN in a user namespace and construct the required HFSC hierarchy, enabling kernel data access, control-flow hijacking, or a panic.

CVSS severity7.8
High
EPSS probability0.21%
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 2.6.12 and later HFSC schedulers allows local users to compromise the kernel through traffic-control operations. The hfsc_dequeue() path can leave a freed hfsc_class linked in the eligible tree when a child qdisc returns no packet, then dereference the reclaimed class. A local user can obtain CAP_NET_ADMIN in a user namespace and construct the required HFSC hierarchy, enabling kernel data access, control-flow hijacking, or a panic.

The record

CVE
CVE-2025-37823
Published
May 8, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 8, 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=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <11bccb054c1462fb069219f8e98e97a5a730758e
  2. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <2f46d14919c39528c6e540ebc43f90055993eedc
  3. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <68f256305ceb426d545a0dc31f83c2ab1d211a1e
  4. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <6ccbda44e2cc3d26fd22af54c650d6d5d801addf
  5. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <76c4c22c2437d3d3880efc0f62eca06ef078d290
  6. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <c6936266f8bf98a53f28ef9a820e6a501e946d09
  7. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <c6f035044104c6ff656f4565cd22938dc892528c
  8. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <da7936518996d290e2fcfcaf6cd7e15bfd87804a
  9. Affected versionversion=2.6.12

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <11bccb054c1462fb069219f8e98e97a5a730758e; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <2f46d14919c39528c6e540ebc43f90055993eedc; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <68f256305ceb426d545a0dc31f83c2ab1d211a1e; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <6ccbda44e2cc3d26fd22af54c650d6d5d801addf; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <76c4c22c2437d3d3880efc0f62eca06ef078d290; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <c6936266f8bf98a53f28ef9a820e6a501e946d09; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <c6f035044104c6ff656f4565cd22938dc892528c; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <da7936518996d290e2fcfcaf6cd7e15bfd87804a; version=2.6.12

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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

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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