{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-64109","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-07-19T07:54:57.034Z","datePublished":"2026-07-19T15:40:11.510Z","dateUpdated":"2026-08-05T12:39:18.983Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-05T12:39:18.983Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\naf_unix: Fix UAF read of tail->len in unix_stream_data_wait()\n\nunix_stream_data_wait() does skb_peek_tail(&sk->sk_receive_queue) without\nholding any lock that prevents SKBs on that queue from being dequeued and\nfreed.\nThis has been the case since commit 79f632c71bea (\"unix/stream: fix\npeeking with an offset larger than data in queue\").\nThe first consequence of this is that the pointer comparison\n`tail != last` can be false even if `last` semantically refers to an\nalready-freed SKB while `tail` is a new SKB allocated at the same address;\nwhich can cause unix_stream_data_wait() to wrongly keep blocking after new\ndata has arrived, but only in a weird scenario where a peeking recv() and\na normal recv() on the same socket are racing, which is probably not a\nreal problem.\n\nBut since commit 2b514574f7e8 (\"net: af_unix: implement splice for stream\naf_unix sockets\"), `tail` is actually dereferenced, which can cause UAF in\nthe following race scenario (where test_setup() runs single-threaded,\nand afterwards, test_thread1() and test_thread2() run concurrently in\ntwo threads:\n```\nstatic int socks[2];\nvoid test_setup(void) {\n  socketpair(AF_UNIX, SOCK_STREAM, 0, socks);\n  send(socks[1], \"A\", 1, 0);\n  int peekoff = 1;\n  setsockopt(socks[0], SOL_SOCKET, SO_PEEK_OFF, &peekoff, sizeof(peekoff));\n}\nvoid test_thread1(void) {\n  char dummy;\n  recv(socks[0], &dummy, 1, MSG_PEEK);\n}\nvoid test_thread2(void) {\n  char dummy;\n  recv(socks[0], &dummy, 1, 0);\n  shutdown(socks[1], SHUT_WR);\n}\n```\n\nwhen racing like this:\n```\nthread1                       thread2\nunix_stream_read_generic\n  mutex_lock(&u->iolock)\n  skb_peek(&sk->sk_receive_queue)\n  skb_peek_next(skb, &sk->sk_receive_queue)\n  mutex_unlock(&u->iolock)\n                              unix_stream_read_generic\n                                unix_state_lock(sk)\n                                skb_peek(&sk->sk_receive_queue)\n                                unix_state_unlock(sk)\n  unix_stream_data_wait\n    unix_state_lock(sk)\n    tail = skb_peek_tail(&sk->sk_receive_queue)\n                                spin_lock(&sk->sk_receive_queue.lock)\n                                __skb_unlink(skb, &sk->sk_receive_queue)\n                                spin_unlock(&sk->sk_receive_queue.lock)\n                                consume_skb(skb) [frees the SKB]\n    `tail != last`: false\n    `tail`: true\n    `tail->len != last_len` ***UAF***\n```\n\nFix the UAF by removing the read of tail->len; checking tail->len would\nonly make sense if SKBs in the receive queue of a UNIX socket could grow,\nwhich can no longer happen.\n\nKuniyuki explained:\n\n> When commit 869e7c62486e (\"net: af_unix: implement stream sendpage\n> support\") added sendpage() support, data could be appended to the last\n> skb in the receiver's queue.\n>\n> That's why we needed to check if the length of the last skb was changed\n> while waiting for new data in unix_stream_data_wait().\n>\n> However, commit a0dbf5f818f9 (\"af_unix: Support MSG_SPLICE_PAGES\") and\n> commit 57d44a354a43 (\"unix: Convert unix_stream_sendpage() to use\n> MSG_SPLICE_PAGES\") refactored sendmsg(), and now data is always added\n> to a new skb.\n\nThat means this fix is not suitable for kernels before 6.5."}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","baseScore":8.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The bug is reached only through local syscalls on AF_UNIX SOCK_STREAM sockets (recvmsg, splice_read, setsockopt SO_PEEK_OFF), not via any network protocol handler.\nAC:L - The attacker controls both racing threads on the same socket fd and can retry the peek/normal-recv interleaving; this is a self-induced race, not one dependent on uncontrollable kernel state.\nPR:L - Any unprivileged local user can create AF_UNIX socketpairs, set SO_PEEK_OFF, and run concurrent recv operations without capabilities, including from within user namespaces.\nUI:N - Exploitation requires no victim interaction; the attacker sets up and races their own socket endpoints programmatically.\nS:C - Successful kernel heap UAF exploitation from an unprivileged container, Android app sandbox, or user-namespace tenant crosses the sandbox boundary to compromise the host kernel.\nC:H - This is a slab use-after-free read of sk_buff->len on freed memory, which per UAF guidance enables arbitrary kernel memory disclosure and heap layout leaks.\nI:H - UAF on sk_buff objects in the kernel heap can be leveraged through heap grooming and spraying to obtain arbitrary write and kernel code execution primitives.\nA:H - The UAF read can trigger KASAN slab-use-after-free faults, kernel oops, or panic during the dereference, and repeated triggering causes denial of service."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/unix/af_unix.c"],"versions":[{"version":"2b514574f7e88c8498027ee366fd6e7aae5aa4b5","lessThan":"26342087fac93b3932e6af61dc91ec029cb8a623","status":"affected","versionType":"git"},{"version":"2b514574f7e88c8498027ee366fd6e7aae5aa4b5","lessThan":"38bccb927d83d7d52e5b20015a172a0b6101d11e","status":"affected","versionType":"git"},{"version":"2b514574f7e88c8498027ee366fd6e7aae5aa4b5","lessThan":"acdff9907478e82208475b1151700d0b71dcdc63","status":"affected","versionType":"git"},{"version":"2b514574f7e88c8498027ee366fd6e7aae5aa4b5","lessThan":"5f162f95a95834f06a8ec6140889272ad12e842f","status":"affected","versionType":"git"},{"version":"2b514574f7e88c8498027ee366fd6e7aae5aa4b5","lessThan":"be309f8eae8b474a4a617eaae01324da996fc719","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/unix/af_unix.c"],"versions":[{"version":"4.2","status":"affected"},{"version":"0","lessThan":"4.2","status":"unaffected","versionType":"semver"},{"version":"6.6.143","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.92","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.34","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.0.11","lessThanOrEqual":"7.0.*","status":"unaffected","versionType":"semver"},{"version":"7.1","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.2","versionEndExcluding":"6.6.143"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.2","versionEndExcluding":"6.12.92"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.2","versionEndExcluding":"6.18.34"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.2","versionEndExcluding":"7.0.11"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.2","versionEndExcluding":"7.1"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/26342087fac93b3932e6af61dc91ec029cb8a623"},{"url":"https://git.kernel.org/stable/c/38bccb927d83d7d52e5b20015a172a0b6101d11e"},{"url":"https://git.kernel.org/stable/c/acdff9907478e82208475b1151700d0b71dcdc63"},{"url":"https://git.kernel.org/stable/c/5f162f95a95834f06a8ec6140889272ad12e842f"},{"url":"https://git.kernel.org/stable/c/be309f8eae8b474a4a617eaae01324da996fc719"}],"title":"af_unix: Fix UAF read of tail->len in unix_stream_data_wait()","x_generator":{"engine":"bippy-1.2.0"}}}}