{"cve":"CVE-2024-26676","nvd":{"published":"2024-04-02T07:15:44.170","modified":"2026-06-17T07:18:04.210","status":"Undergoing Analysis","description":"In the Linux kernel, the following vulnerability has been resolved:\n\naf_unix: Call kfree_skb() for dead unix_(sk)->oob_skb in GC.\n\nsyzbot reported a warning [0] in __unix_gc() with a repro, which\ncreates a socketpair and sends one socket's fd to itself using the\npeer.\n\n  socketpair(AF_UNIX, SOCK_STREAM, 0, [3, 4]) = 0\n  sendmsg(4, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base=\"\\360\", iov_len=1}],\n          msg_iovlen=1, msg_control=[{cmsg_len=20, cmsg_level=SOL_SOCKET,\n                                      cmsg_type=SCM_RIGHTS, cmsg_data=[3]}],\n          msg_controllen=24, msg_flags=0}, MSG_OOB|MSG_PROBE|MSG_DONTWAIT|MSG_ZEROCOPY) = 1\n\nThis forms a self-cyclic reference that GC should finally untangle\nbut does not due to lack of MSG_OOB handling, resulting in memory\nleak.\n\nRecently, commit 11498715f266 (\"af_unix: Remove io_uring code for\nGC.\") removed io_uring's dead code in GC and revealed the problem.\n\nThe code was executed at the final stage of GC and unconditionally\nmoved all GC candidates from gc_candidates to gc_inflight_list.\nThat papered over the reported problem by always making the following\nWARN_ON_ONCE(!list_empty(&gc_candidates)) false.\n\nThe problem has been there since commit 2aab4b969002 (\"af_unix: fix\nstruct pid leaks in OOB support\") added full scm support for MSG_OOB\nwhile fixing another bug.\n\nTo fix this problem, we must call kfree_skb() for unix_sk(sk)->oob_skb\nif the socket still exists in gc_candidates after purging collected skb.\n\nThen, we need to set NULL to oob_skb before calling kfree_skb() because\nit calls last fput() and triggers unix_release_sock(), where we call\nduplicate kfree_skb(u->oob_skb) if not NULL.\n\nNote that the leaked socket remained being linked to a global list, so\nkmemleak also could not detect it.  We need to check /proc/net/protocol\nto notice the unfreed socket.\n\n[0]:\nWARNING: CPU: 0 PID: 2863 at net/unix/garbage.c:345 __unix_gc+0xc74/0xe80 net/unix/garbage.c:345\nModules linked in:\nCPU: 0 PID: 2863 Comm: kworker/u4:11 Not tainted 6.8.0-rc1-syzkaller-00583-g1701940b1a02 #0\nHardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024\nWorkqueue: events_unbound __unix_gc\nRIP: 0010:__unix_gc+0xc74/0xe80 net/unix/garbage.c:345\nCode: 8b 5c 24 50 e9 86 f8 ff ff e8 f8 e4 22 f8 31 d2 48 c7 c6 30 6a 69 89 4c 89 ef e8 97 ef ff ff e9 80 f9 ff ff e8 dd e4 22 f8 90 <0f> 0b 90 e9 7b fd ff ff 48 89 df e8 5c e7 7c f8 e9 d3 f8 ff ff e8\nRSP: 0018:ffffc9000b03fba0 EFLAGS: 00010293\nRAX: 0000000000000000 RBX: ffffc9000b03fc10 RCX: ffffffff816c493e\nRDX: ffff88802c02d940 RSI: ffffffff896982f3 RDI: ffffc9000b03fb30\nRBP: ffffc9000b03fce0 R08: 0000000000000001 R09: fffff52001607f66\nR10: 0000000000000003 R11: 0000000000000002 R12: dffffc0000000000\nR13: ffffc9000b03fc10 R14: ffffc9000b03fc10 R15: 0000000000000001\nFS:  0000000000000000(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000\nCS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\nCR2: 00005559c8677a60 CR3: 000000000d57a000 CR4: 00000000003506f0\nDR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000\nDR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400\nCall Trace:\n <TASK>\n process_one_work+0x889/0x15e0 kernel/workqueue.c:2633\n process_scheduled_works kernel/workqueue.c:2706 [inline]\n worker_thread+0x8b9/0x12a0 kernel/workqueue.c:2787\n kthread+0x2c6/0x3b0 kernel/kthread.c:388\n ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147\n ret_from_fork_asm+0x1b/0x30 arch/x86/entry/entry_64.S:242\n </TASK>","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","score":5.5},"cwes":["CWE-401"],"references":["https://git.kernel.org/stable/c/1279f9d9dec2d7462823a18c29ad61359e0a007d","https://git.kernel.org/stable/c/4fe505c63aa3273135a57597fda761e9aecc7668","https://git.kernel.org/stable/c/82ae47c5c3a6b27fdc0f9e83c1499cb439c56140","https://git.kernel.org/stable/c/b74aa9ce13d02b7fd37c5325b99854f91b9b4276","https://git.kernel.org/stable/c/e0e09186d8821ad59806115d347ea32efa43ca4b"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T21:47:51.568503435+00:00"},"epss":{"cve":"CVE-2024-26676","score":0.00231,"percentile":0.13949,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}