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CVE-2026-46116

Estado: En análisisAlta (7.8)—

In 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:

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.

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__xfrm_state_delete() guards its byseq and byspi unhashes with value-based predicates:

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:

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:

Detalles técnicos trazas, registros y código del informe original
  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

	if (x->km.seq)
		hlist_del_rcu(&x->byseq);
	if (x->id.spi)
		hlist_del_rcu(&x->byspi);

  - 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.

  - 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

CVSS

Probabilidad de explotación (EPSS)

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

🎯 Técnicas ATT&CK

Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.

Vulnerabilidad de uso después de liberación (CWE-416) en código del kernel con acceso local (AV:L, PR:L). Permite ejecución arbitraria de código en contexto de kernel. DoS también posible por corrupción de memoria.

Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.

🛡️ Mitigaciones ATT&CK que cubren estas técnicas

Execution PreventionThreat Intelligence ProgramRestrict Web-Based ContentPrivileged Account ManagementLimit Software InstallationFilter Network Traffic

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

Referencias

JSON original (NVD)

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  ],
  "vulnStatus": "Undergoing Analysis",
  "weaknesses": [
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      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
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          "lang": "en",
          "value": "CWE-416"
        }
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      "description": [
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          "value": "CWE-763"
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  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nxfrm: defensively unhash xfrm_state lists in __xfrm_state_delete\n\nKASAN reproduces a slab-use-after-free in __xfrm_state_delete()'s\nhlist_del_rcu calls under syzkaller load on linux-6.12.y stable\n(reproduced on 6.12.47, also reachable via the same code path on\ntorvalds/master and on the ipsec tree). Nine unique signatures cluster\nin the xfrm_state lifecycle, the load-bearing one being:\n\n  BUG: KASAN: slab-use-after-free in __hlist_del include/linux/list.h:990 [inline]\n  BUG: KASAN: slab-use-after-free in hlist_del_rcu include/linux/rculist.h:516 [inline]\n  BUG: KASAN: slab-use-after-free in __xfrm_state_delete net/xfrm/xfrm_state.c\n  Write of size 8 at addr ffff8881198bcb70 by task kworker/u8:9/435\n\n  Workqueue: netns cleanup_net\n  Call Trace:\n   __hlist_del / hlist_del_rcu\n   __xfrm_state_delete\n   xfrm_state_delete\n   xfrm_state_flush\n   xfrm_state_fini\n   ops_exit_list\n   cleanup_net\n\nThe other observed signatures hit the same slab object from\n__xfrm_state_lookup, xfrm_alloc_spi, __xfrm_state_insert and an OOB\nwrite variant of __xfrm_state_delete, all on the byseq/byspi\nhash chains.\n\n__xfrm_state_delete() guards its byseq and byspi unhashes with\nvalue-based predicates:\n\n\tif (x->km.seq)\n\t\thlist_del_rcu(&x->byseq);\n\tif (x->id.spi)\n\t\thlist_del_rcu(&x->byspi);\n\nwhile everywhere else in the file (e.g. state_cache, state_cache_input)\nthe safer hlist_unhashed() check is used. xfrm_alloc_spi() sets\nx->id.spi = newspi inside xfrm_state_lock and then immediately inserts\ninto byspi, but a path that observes x->id.spi != 0 outside of\nxfrm_state_lock can still skip-or-hit the byspi unhash inconsistently\nwith whether x is actually on the list. The same holds for x->km.seq\nversus byseq, and the bydst/bysrc unhashes have no predicate at all,\nso a second __xfrm_state_delete() on the same object writes through\nLIST_POISON pprev.\n\nThe defensive change here:\n\n  - Use hlist_del_init_rcu() instead of hlist_del_rcu() on bydst,\n    bysrc, byseq and byspi so a second deletion is a no-op rather\n    than a write through LIST_POISON pprev. The byseq/byspi nodes\n    are already initialised in xfrm_state_alloc().\n  - Test hlist_unhashed() rather than the value predicate for\n    byseq/byspi, so the unhash decision tracks list state rather than\n    mutable scalar fields.\n\nEmpirical verification: applied this patch on top of v6.12.47, rebuilt,\nand re-ran the same syzkaller harness for 1h16m on a previously-crashy\nconfiguration that produced ~100 hits each of slab-use-after-free\nRead in xfrm_alloc_spi / Read in __xfrm_state_lookup / Write in\n__xfrm_state_delete. After the patch, 7.1M execs across 32 VMs at\n~1550 exec/sec produced zero xfrm_state UAF/OOB hits. /proc/slabinfo\nconfirms the xfrm_state slab is actively allocated and freed during\nthe run (~143 KiB resident), so the fuzzer is still exercising those\ncode paths -- they just no longer crash.\n\nReproduction:\n\n  - Linux 6.12.47 x86_64 + KASAN_GENERIC + KASAN_INLINE + KCOV\n  - syzkaller @ 746545b8b1e4c3a128db8652b340d3df90ce61db\n  - 32 QEMU/KVM VMs x 2 vCPU on AWS c5.metal bare metal\n  - 9 unique signatures collected in ~9h, all within xfrm_state\n    lifecycle"
    }
  ],
  "lastModified": "2026-09-15T12:17:49.593",
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