CVE-2026-64109
Full vulnerability record from the local CVENow database.
Description
In the Linux kernel, the following vulnerability has been resolved: af_unix: Fix UAF read of tail->len in unix_stream_data_wait() unix_stream_data_wait() does skb_peek_tail(&sk->sk_receive_queue) without holding any lock that prevents SKBs on that queue from being dequeued and freed. This has been the case since commit 79f632c71bea ("unix/stream: fix peeking with an offset larger than data in queue"). The first consequence of this is that the pointer comparison `tail != last` can be false even if `last` semantically refers to an already-freed SKB while `tail` is a new SKB allocated at the same address; which can cause unix_stream_data_wait() to wrongly keep blocking after new data has arrived, but only in a weird scenario where a peeking recv() and a normal recv() on the same socket are racing, which is probably not a real problem. But since commit 2b514574f7e8 ("net: af_unix: implement splice for stream af_unix sockets"), `tail` is actually dereferenced, which can cause UAF in the following race scenario (where test_setup() runs single-threaded, and afterwards, test_thread1() and test_thread2() run concurrently in two threads: ``` static int socks[2]; void test_setup(void) { socketpair(AF_UNIX, SOCK_STREAM, 0, socks); send(socks[1], "A", 1, 0); int peekoff = 1; setsockopt(socks[0], SOL_SOCKET, SO_PEEK_OFF, &peekoff, sizeof(peekoff)); } void test_thread1(void) { char dummy; recv(socks[0], &dummy, 1, MSG_PEEK); } void test_thread2(void) { char dummy; recv(socks[0], &dummy, 1, 0); shutdown(socks[1], SHUT_WR); } ``` when racing like this: ``` thread1 thread2 unix_stream_read_generic mutex_lock(&u->iolock) skb_peek(&sk->sk_receive_queue) skb_peek_next(skb, &sk->sk_receive_queue) mutex_unlock(&u->iolock) unix_stream_read_generic unix_state_lock(sk) skb_peek(&sk->sk_receive_queue) unix_state_unlock(sk) unix_stream_data_wait unix_state_lock(sk) tail = skb_peek_tail(&sk->sk_receive_queue) spin_lock(&sk->sk_receive_queue.lock) __skb_unlink(skb, &sk->sk_receive_queue) spin_unlock(&sk->sk_receive_queue.lock) consume_skb(skb) [frees the SKB] `tail != last`: false `tail`: true `tail->len != last_len` ***UAF*** ``` Fix the UAF by removing the read of tail->len; checking tail->len would only make sense if SKBs in the receive queue of a UNIX socket could grow, which can no longer happen. Kuniyuki explained: > When commit 869e7c62486e ("net: af_unix: implement stream sendpage > support") added sendpage() support, data could be appended to the last > skb in the receiver's queue. > > That's why we needed to check if the length of the last skb was changed > while waiting for new data in unix_stream_data_wait(). > > However, commit a0dbf5f818f9 ("af_unix: Support MSG_SPLICE_PAGES") and > commit 57d44a354a43 ("unix: Convert unix_stream_sendpage() to use > MSG_SPLICE_PAGES") refactored sendmsg(), and now data is always added > to a new skb. That means this fix is not suitable for kernels before 6.5.
View original CVE JSON
{
"id": "CVE-2026-64109",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2026-07-19T16:17:52.233",
"lastModified": "2026-10-19T21:17:23.517",
"vulnStatus": "Modified",
"cveTags": [],
"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."
}
],
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "unaffected",
"programFiles": [
"net/unix/af_unix.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"versions": [
{
"version": "2b514574f7e88c8498027ee366fd6e7aae5aa4b5",
"lessThan": "26342087fac93b3932e6af61dc91ec029cb8a623",
"versionType": "git",
"status": "affected"
},
{
"version": "2b514574f7e88c8498027ee366fd6e7aae5aa4b5",
"lessThan": "38bccb927d83d7d52e5b20015a172a0b6101d11e",
"versionType": "git",
"status": "affected"
},
{
"version": "2b514574f7e88c8498027ee366fd6e7aae5aa4b5",
"lessThan": "acdff9907478e82208475b1151700d0b71dcdc63",
"versionType": "git",
"status": "affected"
},
{
"version": "2b514574f7e88c8498027ee366fd6e7aae5aa4b5",
"lessThan": "5f162f95a95834f06a8ec6140889272ad12e842f",
"versionType": "git",
"status": "affected"
},
{
"version": "2b514574f7e88c8498027ee366fd6e7aae5aa4b5",
"lessThan": "be309f8eae8b474a4a617eaae01324da996fc719",
"versionType": "git",
"status": "affected"
}
]
},
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "affected",
"programFiles": [
"net/unix/af_unix.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"versions": [
{
"version": "4.2",
"status": "affected"
},
{
"version": "0",
"lessThan": "4.2",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.6.143",
"lessThanOrEqual": "6.6.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.12.92",
"lessThanOrEqual": "6.12.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.18.34",
"lessThanOrEqual": "6.18.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "7.0.11",
"lessThanOrEqual": "7.0.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "7.1",
"lessThanOrEqual": "*",
"versionType": "original_commit_for_fix",
"status": "unaffected"
}
]
}
]
}
],
"metrics": {
"cvssMetricV31": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"type": "Secondary",
"cvssData": {
"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",
"attackVector": "LOCAL",
"attackComplexity": "LOW",
"privilegesRequired": "LOW",
"userInteraction": "NONE",
"scope": "CHANGED",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"availabilityImpact": "HIGH"
},
"exploitabilityScore": 2.0,
"impactScore": 6.0
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"timestamp": "2026-10-16T15:36:24.265690Z",
"id": "CVE-2026-64109",
"options": [
{
"exploitation": "none"
},
{
"automatable": "no"
},
{
"technicalImpact": "total"
}
],
"role": "CISA Coordinator",
"version": "2.0.3"
}
}
]
},
"weaknesses": [
{
"source": "[email protected]",
"type": "Primary",
"description": [
{
"lang": "en",
"value": "CWE-416"
}
]
},
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"type": "Secondary",
"description": [
{
"lang": "en",
"value": "CWE-416"
}
]
}
],
"configurations": [
{
"nodes": [
{
"operator": "OR",
"negate": false,
"cpeMatch": [
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "4.2",
"versionEndExcluding": "6.6.143",
"matchCriteriaId": "AABBF625-2FE9-43D0-9CD6-9A6B699FA975"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "6.7",
"versionEndExcluding": "6.12.92",
"matchCriteriaId": "9CB90BD9-95B7-4D7F-9F17-4ECE6CFB66C9"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "6.13",
"versionEndExcluding": "6.18.34",
"matchCriteriaId": "A4B1EF6D-18D7-4838-BC37-7499D5DCC3C0"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "6.19",
"versionEndExcluding": "7.0.11",
"matchCriteriaId": "0520D091-FC52-4A50-AF07-70AE7D08B750"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:7.1:rc1:*:*:*:*:*:*",
"matchCriteriaId": "B1EF7059-E670-45F4-B422-54C40FA86390"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:7.1:rc2:*:*:*:*:*:*",
"matchCriteriaId": "0D38F0BF-A728-4133-A358-D44A2F7EE6D6"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:7.1:rc3:*:*:*:*:*:*",
"matchCriteriaId": "EC732D08-5F7B-46D9-B154-E60C7F4F0A97"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:7.1:rc4:*:*:*:*:*:*",
"matchCriteriaId": "E5910A9D-F60A-409A-B486-FE66BFEBA9B9"
}
]
}
]
}
],
"references": [
{
"url": "https://git.kernel.org/stable/c/26342087fac93b3932e6af61dc91ec029cb8a623",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
]
},
{
"url": "https://git.kernel.org/stable/c/38bccb927d83d7d52e5b20015a172a0b6101d11e",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
]
},
{
"url": "https://git.kernel.org/stable/c/5f162f95a95834f06a8ec6140889272ad12e842f",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
]
},
{
"url": "https://git.kernel.org/stable/c/acdff9907478e82208475b1151700d0b71dcdc63",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
]
},
{
"url": "https://git.kernel.org/stable/c/be309f8eae8b474a4a617eaae01324da996fc719",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
]
}
]
}