{ "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" } } } }