xfrm: defensively unhash xfrm_state lists in __xfrm_state_delete

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Summary

CVECVE-2026-46116
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-28 10:16:27 UTC
Updated2026-07-07 12:16:52 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: xfrm: defensively unhash xfrm_state lists in __xfrm_state_delete KASAN reproduces a slab-use-after-free in __xfrm_state_delete()'s hlist_del_rcu calls under syzkaller load on linux-6.12.y stable (reproduced on 6.12.47, also reachable via the same code path on torvalds/master and on the ipsec tree). Nine unique signatures cluster in the xfrm_state lifecycle, the load-bearing one being: BUG: KASAN: slab-use-after-free in __hlist_del include/linux/list.h:990 [inline] BUG: KASAN: slab-use-after-free in hlist_del_rcu include/linux/rculist.h:516 [inline] BUG: KASAN: slab-use-after-free in __xfrm_state_delete net/xfrm/xfrm_state.c Write of size 8 at addr ffff8881198bcb70 by task kworker/u8:9/435 Workqueue: netns cleanup_net Call Trace: __hlist_del / hlist_del_rcu __xfrm_state_delete xfrm_state_delete xfrm_state_flush xfrm_state_fini ops_exit_list cleanup_net The other observed signatures hit the same slab object from __xfrm_state_lookup, xfrm_alloc_spi, __xfrm_state_insert and an OOB write variant of __xfrm_state_delete, all on the byseq/byspi hash chains. __xfrm_state_delete() guards its byseq and byspi unhashes with value-based predicates: if (x->km.seq) hlist_del_rcu(&x->byseq); if (x->id.spi) hlist_del_rcu(&x->byspi); while everywhere else in the file (e.g. state_cache, state_cache_input) the safer hlist_unhashed() check is used. xfrm_alloc_spi() sets x->id.spi = newspi inside xfrm_state_lock and then immediately inserts into byspi, but a path that observes x->id.spi != 0 outside of xfrm_state_lock can still skip-or-hit the byspi unhash inconsistently with whether x is actually on the list. The same holds for x->km.seq versus byseq, and the bydst/bysrc unhashes have no predicate at all, so a second __xfrm_state_delete() on the same object writes through LIST_POISON pprev. The defensive change here: - Use hlist_del_init_rcu() instead of hlist_del_rcu() on bydst, bysrc, byseq and byspi so a second deletion is a no-op rather than a write through LIST_POISON pprev. The byseq/byspi nodes are already initialised in xfrm_state_alloc(). - Test hlist_unhashed() rather than the value predicate for byseq/byspi, so the unhash decision tracks list state rather than mutable scalar fields. Empirical verification: applied this patch on top of v6.12.47, rebuilt, and re-ran the same syzkaller harness for 1h16m on a previously-crashy configuration that produced ~100 hits each of slab-use-after-free Read in xfrm_alloc_spi / Read in __xfrm_state_lookup / Write in __xfrm_state_delete. After the patch, 7.1M execs across 32 VMs at ~1550 exec/sec produced zero xfrm_state UAF/OOB hits. /proc/slabinfo confirms the xfrm_state slab is actively allocated and freed during the run (~143 KiB resident), so the fuzzer is still exercising those code paths -- they just no longer crash. Reproduction: - Linux 6.12.47 x86_64 + KASAN_GENERIC + KASAN_INLINE + KCOV - syzkaller @ 746545b8b1e4c3a128db8652b340d3df90ce61db - 32 QEMU/KVM VMs x 2 vCPU on AWS c5.metal bare metal - 9 unique signatures collected in ~9h, all within xfrm_state lifecycle

Risk And Classification

Primary CVSS: v3.1 7 HIGH from ADP

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

EPSS: 0.001260000 probability, percentile 0.025630000 (date 2026-06-24)

Problem Types: CWE-416 | CWE-763 | CWE-763 Release of Invalid Pointer or Reference

VersionSourceTypeScoreSeverityVector
3.1ADPCVSS7HIGHCVSS:3.1/AV:L/AC:H/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
3.10b0ca135-0b70-47e7-9f44-1890c2a1c46cSecondary7HIGHCVSS:3.1/AV:L/AC:H/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
High
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:H/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 7b4dc3600e4877178ba94c7fbf7e520421378aa6 3943fcad7694a7d0b15aeabe7d3cc2a2eb8e92e8 git Not specified
CNA Linux Linux affected 7b4dc3600e4877178ba94c7fbf7e520421378aa6 2c617848ae6e4f07a3e397f604208c293bbecacc git Not specified
CNA Linux Linux affected 7b4dc3600e4877178ba94c7fbf7e520421378aa6 b4a53add2fa8f1b5aa17d4c5686c320785fab182 git Not specified
CNA Linux Linux affected 7b4dc3600e4877178ba94c7fbf7e520421378aa6 26edb0a3c99f9d958c212be68b21f1221614dcf0 git Not specified
CNA Linux Linux affected 7b4dc3600e4877178ba94c7fbf7e520421378aa6 4980162de555cb838f1a189ce7d2cbf5d2e7b050 git Not specified
CNA Linux Linux affected 7b4dc3600e4877178ba94c7fbf7e520421378aa6 a2e2d08fb070fab4947447171f1c4e3ca5a188e5 git Not specified
CNA Linux Linux affected 7b4dc3600e4877178ba94c7fbf7e520421378aa6 14acf9652e5690de3c7486c6db5fb8dafd0a32a3 git Not specified
CNA Linux Linux affected 2.6.19 Not specified
CNA Linux Linux unaffected 2.6.19 semver Not specified
CNA Linux Linux unaffected 5.15.210 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.176 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.140 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.88 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.30 6.18.* semver Not specified
CNA Linux Linux unaffected 7.0.7 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1 * original_commit_for_fix Not specified
ADP Red Hat Red Hat Enterprise Linux AppStream V. 9 Not specified Not specified
ADP Red Hat Red Hat Enterprise Linux BaseOS V. 9 Not specified Not specified
ADP Red Hat Red Hat Enterprise Linux CodeReady Linux Builder V. 9 Not specified Not specified
ADP Red Hat Red Hat Enterprise Linux Real Time For NFV V. 9 Not specified Not specified
ADP Red Hat Red Hat Enterprise Linux Real Time V. 9 Not specified Not specified
ADP Red Hat Red Hat Enterprise Linux 10 Not specified Not specified
ADP Red Hat Red Hat Enterprise Linux 7 Not specified Not specified
ADP Red Hat Red Hat Enterprise Linux 8 Not specified Not specified
ADP Red Hat Red Hat Enterprise Linux 9 Not specified Not specified
ADP Red Hat Red Hat Enterprise Linux 6 Not specified Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/a2e2d08fb070fab4947447171f1c4e3ca5a188e5 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
access.redhat.com/security/cve/CVE-2026-46116 0b0ca135-0b70-47e7-9f44-1890c2a1c46c access.redhat.com
security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-46116.json 0b0ca135-0b70-47e7-9f44-1890c2a1c46c security.access.redhat.com
git.kernel.org/stable/c/3943fcad7694a7d0b15aeabe7d3cc2a2eb8e92e8 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/26edb0a3c99f9d958c212be68b21f1221614dcf0 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
bugzilla.redhat.com/show_bug.cgi 0b0ca135-0b70-47e7-9f44-1890c2a1c46c bugzilla.redhat.com
git.kernel.org/stable/c/4980162de555cb838f1a189ce7d2cbf5d2e7b050 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/14acf9652e5690de3c7486c6db5fb8dafd0a32a3 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/b4a53add2fa8f1b5aa17d4c5686c320785fab182 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/2c617848ae6e4f07a3e397f604208c293bbecacc 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
access.redhat.com/errata/RHSA-2026:36018 0b0ca135-0b70-47e7-9f44-1890c2a1c46c access.redhat.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Additional Advisory Data

SourceTimeEvent
ADP2026-05-28T00:00:00.000ZReported to Red Hat.
ADP2026-05-28T00:00:00.000ZMade public.

Solutions

ADP: RHSA-2026:36018: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux BaseOS (v. 9), Red Hat Enterprise Linux CodeReady Linux Builder (v. 9), Red Hat Enterprise Linux Real Time (v. 9), Red Hat Enterprise Linux Real Time for NFV (v. 9)

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