{"id":"CVE-2026-22977","title":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: sock: fix hardened usercopy panic in sock_recv_errqueue\n\nskbuff_fclone_cache was created without defining a usercopy region,\n[1] unlike skbuff_head_cache which pro…","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: sock: fix hardened usercopy panic in sock_recv_errqueue\n\nskbuff_fclone_cache was created without defining a usercopy region,\n[1] unlike skbuff_head_cache which pro…","severity":"medium","cvss":5.5,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","cwe":["CWE-476"],"vendor":"linux","product":"linux_kernel","affected":["linux_kernel >= 4.16, < 5.10.248","linux_kernel >= 5.11, < 5.15.198","linux_kernel >= 5.16, < 6.1.161","linux_kernel >= 6.2, < 6.6.121","linux_kernel >= 6.7, < 6.12.66","linux_kernel >= 6.13, < 6.18.6","linux_kernel = 6.19"],"patched":["linux_kernel 6.18.6"],"published":"2026-01-21","updated":"2026-10-15","sourceUpdated":"2026-10-15T02:18:38.050","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-22977","references":[{"url":"https://git.kernel.org/stable/c/005671c60fcf1dbdb8bddf12a62568fd5e4ec391","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/2a71a1a8d0ed718b1c7a9ac61f07e5755c47ae20","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/582a5e922a9652fcbb7d0165c95d5b20aa37575d","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/88dd6be7ebb3153b662c2cebcb06e032a92857f5","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/8c6901aa29626e35045130bac09b75f791acca85","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/c655d2167bf014d4c61b4faeca59b60ff9b9f6b1","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/e00b169eaac5f7cdbf710c354c8fa76d02009115","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-019113.html","label":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-253495.html","label":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-457936.html","label":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"}],"tags":["nvd","cve.org"],"epss":0.00194,"epssPercentile":0.08981,"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"partial","timestamp":"2026-06-10T20:41:47.988660Z"},"ingestedAt":"2026-09-08T15:33:26.994Z","slug":"CVE-2026-22977","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nnet: sock: fix hardened usercopy panic in sock_recv_errqueue\n\nskbuff_fclone_cache was created without defining a usercopy region,\n[1] unlike skbuff_head_cache which properly whitelists the cb[] field.\n[2] This causes a usercopy BUG() when CONFIG_HARDENED_USERCOPY is\nenabled and the kernel attempts to copy sk_buff.cb data to userspace\nvia sock_recv_errqueue() -> put_cmsg().\n\nThe crash occurs when: 1. TCP allocates an skb using alloc_skb_fclone()\n   (from skbuff_fclone_cache) [1]\n2. The skb is cloned via skb_clone() using the pre-allocated fclone\n[3] 3. The cloned skb is queued to sk_error_queue for timestamp\nreporting 4. Userspace reads the error queue via recvmsg(MSG_ERRQUEUE)\n5. sock_recv_errqueue() calls put_cmsg() to copy serr->ee from skb->cb\n[4] 6. __check_heap_object() fails because skbuff_fclone_cache has no\n   usercopy whitelist [5]\n\nWhen cloned skbs allocated from skbuff_fclone_cache are used in the\nsocket error queue, accessing the sock_exterr_skb structure in skb->cb\nvia put_cmsg() triggers a usercopy hardening violation:\n\n[    5.379589] usercopy: Kernel memory exposure attempt detected from SLUB object 'skbuff_fclone_cache' (offset 296, size 16)!\n[    5.382796] kernel BUG at mm/usercopy.c:102!\n[    5.383923] Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI\n[    5.384903] CPU: 1 UID: 0 PID: 138 Comm: poc_put_cmsg Not tainted 6.12.57 #7\n[    5.384903] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014\n[    5.384903] RIP: 0010:usercopy_abort+0x6c/0x80\n[    5.384903] Code: 1a 86 51 48 c7 c2 40 15 1a 86 41 52 48 c7 c7 c0 15 1a 86 48 0f 45 d6 48 c7 c6 80 15 1a 86 48 89 c1 49 0f 45 f3 e8 84 27 88 ff <0f> 0b 490\n[    5.384903] RSP: 0018:ffffc900006f77a8 EFLAGS: 00010246\n[    5.384903] RAX: 000000000000006f RBX: ffff88800f0ad2a8 RCX: 1ffffffff0f72e74\n[    5.384903] RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffffffff87b973a0\n[    5.384903] RBP: 0000000000000010 R08: 0000000000000000 R09: fffffbfff0f72e74\n[    5.384903] R10: 0000000000000003 R11: 79706f6372657375 R12: 0000000000000001\n[    5.384903] R13: ffff88800f0ad2b8 R14: ffffea00003c2b40 R15: ffffea00003c2b00\n[    5.384903] FS:  0000000011bc4380(0000) GS:ffff8880bf100000(0000) knlGS:0000000000000000\n[    5.384903] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n[    5.384903] CR2: 000056aa3b8e5fe4 CR3: 000000000ea26004 CR4: 0000000000770ef0\n[    5.384903] PKRU: 55555554\n[    5.384903] Call Trace:\n[    5.384903]  <TASK>\n[    5.384903]  __check_heap_object+0x9a/0xd0\n[    5.384903]  __check_object_size+0x46c/0x690\n[    5.384903]  put_cmsg+0x129/0x5e0\n[    5.384903]  sock_recv_errqueue+0x22f/0x380\n[    5.384903]  tls_sw_recvmsg+0x7ed/0x1960\n[    5.384903]  ? srso_alias_return_thunk+0x5/0xfbef5\n[    5.384903]  ? schedule+0x6d/0x270\n[    5.384903]  ? srso_alias_return_thunk+0x5/0xfbef5\n[    5.384903]  ? mutex_unlock+0x81/0xd0\n[    5.384903]  ? __pfx_mutex_unlock+0x10/0x10\n[    5.384903]  ? __pfx_tls_sw_recvmsg+0x10/0x10\n[    5.384903]  ? _raw_spin_lock_irqsave+0x8f/0xf0\n[    5.384903]  ? _raw_read_unlock_irqrestore+0x20/0x40\n[    5.384903]  ? srso_alias_return_thunk+0x5/0xfbef5\n\nThe crash offset 296 corresponds to skb2->cb within skbuff_fclones:\n  - sizeof(struct sk_buff) = 232 - offsetof(struct sk_buff, cb) = 40 -\n  offset of skb2.cb in fclones = 232 + 40 = 272 - crash offset 296 =\n  272 + 24 (inside sock_exterr_skb.ee)\n\nThis patch uses a local stack variable as a bounce buffer to avoid the hardened usercopy check failure.\n\n[1] https://elixir.bootlin.com/linux/v6.12.62/source/net/ipv4/tcp.c#L885\n[2] https://elixir.bootlin.com/linux/v6.12.62/source/net/core/skbuff.c#L5104\n[3] https://elixir.bootlin.com/linux/v6.12.62/source/net/core/skbuff.c#L5566\n[4] https://elixir.bootlin.com/linux/v6.12.62/source/net/core/skbuff.c#L5491\n[5] https://elixir.bootlin.com/linux/v6.12.62/source/mm/slub.c#L5719\n\n## Affected\n\n- `linux_kernel >= 4.16, < 5.10.248`\n- `linux_kernel >= 5.11, < 5.15.198`\n- `linux_kernel >= 5.16, < 6.1.161`\n- `linux_kernel >= 6.2, < 6.6.121`\n- `linux_kernel >= 6.7, < 6.12.66`\n- `linux_kernel >= 6.13, < 6.18.6`\n- `linux_kernel = 6.19`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `linux_kernel 6.18.6`","depth":"sunlit","depthScore":30,"depthScoreParts":{"impact":30.3,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":221589,"id":"CVE-2026-22977","ts":1792035282913,"field":"cvss","old":null,"new":"5.5"},{"seq":221588,"id":"CVE-2026-22977","ts":1792035282913,"field":"severity","old":"none","new":"medium"}]}