CVE-2026-64177
Estado: AnalizadaMedia (5.5)—
In the Linux kernel, the following vulnerability has been resolved:
phonet/pep: disable BH around forwarded sk_receive_skb()
The networking receive path is usually run from softirq context, but protocols that take the socket lock may have packets stored in the backlog and processed later from process context. In that case release_sock() -> __release_sock() drops the slock with spin_unlock_bh() and then calls sk->sk_backlog_rcv() with bottom halves enabled.
Typical sk_backlog_rcv handlers process the socket whose backlog is being drained, so the BH state at entry is irrelevant for the slocks they touch. pep_do_rcv() is different: when the inbound skb targets an existing PEP pipe, it forwards the skb to a different *child* socket via sk_receive_skb().
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That helper takes the child slock with bh_lock_sock_nested(), which is just spin_lock_nested() and assumes BH is already off. The same child slock therefore ends up acquired with BH on (process path) and with BH off (softirq path):
Lockdep flags this as inconsistent lock state, and it can become a real self-deadlock if a softirq on the same CPU tries to receive to the same child socket while its slock is held in the BH-enabled path:
Wrap the forwarded sk_receive_skb() in local_bh_disable() / local_bh_enable() so the child slock is always acquired with BH off. local_bh_disable() nests safely on the softirq path.
Discovered via in-house syzkaller fuzzing; the same root cause also on the linux-6.1.y syzbot dashboard as extid 44f0626dd6284f02663c. Reproduced under KASAN + LOCKDEP + PROVE_LOCKING, reproducer: https://pastebin.com/A3t8xzCR
Detalles técnicos trazas, registros y código del informe original
process context softirq context
--------------- ---------------
release_sock(listener) __netif_receive_skb()
__release_sock() phonet_rcv()
spin_unlock_bh() __sk_receive_skb(listener)
[BH now ENABLED] [BH already disabled]
sk_backlog_rcv: sk_backlog_rcv:
pep_do_rcv() pep_do_rcv()
sk_receive_skb(child) sk_receive_skb(child)
bh_lock_sock_nested(child) bh_lock_sock_nested(child)
=> SOFTIRQ-ON-W => IN-SOFTIRQ-W
WARNING: inconsistent lock state
inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
(slock-AF_PHONET/1){+.?.}-{3:3}, at: __sk_receive_skb+0x1cf/0x900
__sk_receive_skb net/core/sock.c:563
sk_receive_skb include/net/sock.h:2022 [inline]
pep_do_rcv net/phonet/pep.c:675
sk_backlog_rcv include/net/sock.h:1190
__release_sock net/core/sock.c:3216
release_sock net/core/sock.c:3815
pep_sock_accept net/phonet/pep.c:879CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- Puntuación base: 5.5
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.11%
- Percentil entre todas las CVEs puntuadas: 1
- Fecha de la puntuación: 5/10/2026
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).
Tecnologías afectadas (1)
CWE
- NVD-CWE-noinfo
Referencias
- https://git.kernel.org/stable/c/02c04df84de709060f63e1d52ec67488c4f6f212
- https://git.kernel.org/stable/c/8420aa4900417797323dd567ba9d1512280c2dc3
- https://git.kernel.org/stable/c/84bc87beb4cd77670939b446326788e4c9b3db37
- https://git.kernel.org/stable/c/a3fc8f2dacd1c37325977fc1fbbf3d52141df99e
- https://git.kernel.org/stable/c/b2606c302d7f2b4ee48da05e32ed60aed1b0cd53
- https://git.kernel.org/stable/c/bd795f106b3889fb0706c6e4831c4b27e2b5666b
- https://git.kernel.org/stable/c/dbc81608e3a653dea6cf403f20cae35468b8ab9c
- https://git.kernel.org/stable/c/f08c45076e4fd8b0adbc5eb186d6e6a3e7350d7b
JSON original (NVD)
Mostrar
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"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"integrityImpact": "NONE",
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"attackComplexity": "LOW",
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nphonet/pep: disable BH around forwarded sk_receive_skb()\n\nThe networking receive path is usually run from softirq context, but\nprotocols that take the socket lock may have packets stored in the\nbacklog and processed later from process context. In that case\nrelease_sock() -> __release_sock() drops the slock with spin_unlock_bh()\nand then calls sk->sk_backlog_rcv() with bottom halves enabled.\n\nTypical sk_backlog_rcv handlers process the socket whose backlog is\nbeing drained, so the BH state at entry is irrelevant for the slocks\nthey touch. pep_do_rcv() is different: when the inbound skb targets an\nexisting PEP pipe, it forwards the skb to a different *child* socket\nvia sk_receive_skb(). That helper takes the child slock with\nbh_lock_sock_nested(), which is just spin_lock_nested() and assumes BH\nis already off. The same child slock therefore ends up acquired with\nBH on (process path) and with BH off (softirq path):\n\n process context softirq context\n --------------- ---------------\n release_sock(listener) __netif_receive_skb()\n __release_sock() phonet_rcv()\n spin_unlock_bh() __sk_receive_skb(listener)\n [BH now ENABLED] [BH already disabled]\n sk_backlog_rcv: sk_backlog_rcv:\n pep_do_rcv() pep_do_rcv()\n sk_receive_skb(child) sk_receive_skb(child)\n bh_lock_sock_nested(child) bh_lock_sock_nested(child)\n => SOFTIRQ-ON-W => IN-SOFTIRQ-W\n\nLockdep flags this as inconsistent lock state, and it can become a real\nself-deadlock if a softirq on the same CPU tries to receive to the same\nchild socket while its slock is held in the BH-enabled path:\n\n WARNING: inconsistent lock state\n inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.\n (slock-AF_PHONET/1){+.?.}-{3:3}, at: __sk_receive_skb+0x1cf/0x900\n __sk_receive_skb net/core/sock.c:563\n sk_receive_skb include/net/sock.h:2022 [inline]\n pep_do_rcv net/phonet/pep.c:675\n sk_backlog_rcv include/net/sock.h:1190\n __release_sock net/core/sock.c:3216\n release_sock net/core/sock.c:3815\n pep_sock_accept net/phonet/pep.c:879\n\nWrap the forwarded sk_receive_skb() in local_bh_disable() /\nlocal_bh_enable() so the child slock is always acquired with BH off.\nlocal_bh_disable() nests safely on the softirq path.\n\nDiscovered via in-house syzkaller fuzzing; the same root cause also\non the linux-6.1.y syzbot dashboard as extid 44f0626dd6284f02663c.\nReproduced under KASAN + LOCKDEP + PROVE_LOCKING, reproducer:\nhttps://pastebin.com/A3t8xzCR"
}
],
"lastModified": "2026-08-13T15:32:45.440",
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