net_sched: hfsc: Fix a UAF vulnerability in class with netem as child qdisc

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2025-37890
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2025-05-16 13:15:52 UTC
Updated2026-07-30 06:22:28 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: net_sched: hfsc: Fix a UAF vulnerability in class with netem as child qdisc As described in Gerrard's report [1], we have a UAF case when an hfsc class has a netem child qdisc. The crux of the issue is that hfsc is assuming that checking for cl->qdisc->q.qlen == 0 guarantees that it hasn't inserted the class in the vttree or eltree (which is not true for the netem duplicate case). This patch checks the n_active class variable to make sure that the code won't insert the class in the vttree or eltree twice, catering for the reentrant case. [1] https://lore.kernel.org/netdev/CAHcdcOm+03OD2j6R0=YHKqmy=VgJ8xEOKuP6c7mSgnp-TEJJbw@mail.gmail.com/

Risk And Classification

Primary CVSS: v3.1 7.8 HIGH from [email protected]

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Problem Types: CWE-416

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Linux Linux Kernel All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 37d9cf1a3ce35de3df6f7d209bfb1f50cf188cea 273bbcfa53541cde38b2003ad88a59b770306421 git Not specified
CNA Linux Linux affected 37d9cf1a3ce35de3df6f7d209bfb1f50cf188cea e0cf8ee23e1915431f262a7b2dee0c7a7d699af0 git Not specified
CNA Linux Linux affected 37d9cf1a3ce35de3df6f7d209bfb1f50cf188cea e3e949a39a91d1f829a4890e7dfe9417ac72e4d0 git Not specified
CNA Linux Linux affected 37d9cf1a3ce35de3df6f7d209bfb1f50cf188cea 8df7d37d626430035b413b97cee18396b3450bef git Not specified
CNA Linux Linux affected 37d9cf1a3ce35de3df6f7d209bfb1f50cf188cea 6082a87af4c52f58150d40dec1716011d871ac21 git Not specified
CNA Linux Linux affected 37d9cf1a3ce35de3df6f7d209bfb1f50cf188cea 2e7093c7a8aba5d4f8809f271488e5babe75e202 git Not specified
CNA Linux Linux affected 37d9cf1a3ce35de3df6f7d209bfb1f50cf188cea ac39fd4a757584d78ed062d4f6fd913f83bd98b5 git Not specified
CNA Linux Linux affected 37d9cf1a3ce35de3df6f7d209bfb1f50cf188cea 141d34391abbb315d68556b7c67ad97885407547 git Not specified
CNA Linux Linux affected 5.0 Not specified
CNA Linux Linux unaffected 5.0 semver Not specified
CNA Linux Linux unaffected 5.4.294 5.4.* semver Not specified
CNA Linux Linux unaffected 5.10.238 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.182 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.138 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.90 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.28 6.12.* semver Not specified
CNA Linux Linux unaffected 6.14.6 6.14.* semver Not specified
CNA Linux Linux unaffected 6.15 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/141d34391abbb315d68556b7c67ad97885407547 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/ac39fd4a757584d78ed062d4f6fd913f83bd98b5 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/6082a87af4c52f58150d40dec1716011d871ac21 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
lists.debian.org/debian-lts-announce/2025/08/msg00010.html af854a3a-2127-422b-91ae-364da2661108 lists.debian.org Mailing List
git.kernel.org/stable/c/273bbcfa53541cde38b2003ad88a59b770306421 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/e0cf8ee23e1915431f262a7b2dee0c7a7d699af0 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/2e7093c7a8aba5d4f8809f271488e5babe75e202 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/e3e949a39a91d1f829a4890e7dfe9417ac72e4d0 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
lists.debian.org/debian-lts-announce/2025/10/msg00007.html af854a3a-2127-422b-91ae-364da2661108 lists.debian.org Mailing List
git.kernel.org/stable/c/8df7d37d626430035b413b97cee18396b3450bef 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
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