ghsa-wqm2-9j5j-vxv3
Vulnerability from github
In the Linux kernel, the following vulnerability has been resolved:
af_unix: Don't leave consecutive consumed OOB skbs.
Jann Horn reported a use-after-free in unix_stream_read_generic().
The following sequences reproduce the issue:
$ python3 from socket import * s1, s2 = socketpair(AF_UNIX, SOCK_STREAM) s1.send(b'x', MSG_OOB) s2.recv(1, MSG_OOB) # leave a consumed OOB skb s1.send(b'y', MSG_OOB) s2.recv(1, MSG_OOB) # leave a consumed OOB skb s1.send(b'z', MSG_OOB) s2.recv(1) # recv 'z' illegally s2.recv(1, MSG_OOB) # access 'z' skb (use-after-free)
Even though a user reads OOB data, the skb holding the data stays on the recv queue to mark the OOB boundary and break the next recv().
After the last send() in the scenario above, the sk2's recv queue has 2 leading consumed OOB skbs and 1 real OOB skb.
Then, the following happens during the next recv() without MSG_OOB
- unix_stream_read_generic() peeks the first consumed OOB skb
- manage_oob() returns the next consumed OOB skb
- unix_stream_read_generic() fetches the next not-yet-consumed OOB skb
- unix_stream_read_generic() reads and frees the OOB skb
, and the last recv(MSG_OOB) triggers KASAN splat.
The 3. above occurs because of the SO_PEEK_OFF code, which does not expect unix_skb_len(skb) to be 0, but this is true for such consumed OOB skbs.
while (skip >= unix_skb_len(skb)) { skip -= unix_skb_len(skb); skb = skb_peek_next(skb, &sk->sk_receive_queue); ... }
In addition to this use-after-free, there is another issue that ioctl(SIOCATMARK) does not function properly with consecutive consumed OOB skbs.
So, nothing good comes out of such a situation.
Instead of complicating manage_oob(), ioctl() handling, and the next ECONNRESET fix by introducing a loop for consecutive consumed OOB skbs, let's not leave such consecutive OOB unnecessarily.
Now, while receiving an OOB skb in unix_stream_recv_urg(), if its previous skb is a consumed OOB skb, it is freed.
[0]: BUG: KASAN: slab-use-after-free in unix_stream_read_actor (net/unix/af_unix.c:3027) Read of size 4 at addr ffff888106ef2904 by task python3/315
CPU: 2 UID: 0 PID: 315 Comm: python3 Not tainted 6.16.0-rc1-00407-gec315832f6f9 #8 PREEMPT(voluntary) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-4.fc42 04/01/2014 Call Trace: dump_stack_lvl (lib/dump_stack.c:122) print_report (mm/kasan/report.c:409 mm/kasan/report.c:521) kasan_report (mm/kasan/report.c:636) unix_stream_read_actor (net/unix/af_unix.c:3027) unix_stream_read_generic (net/unix/af_unix.c:2708 net/unix/af_unix.c:2847) unix_stream_recvmsg (net/unix/af_unix.c:3048) sock_recvmsg (net/socket.c:1063 (discriminator 20) net/socket.c:1085 (discriminator 20)) __sys_recvfrom (net/socket.c:2278) __x64_sys_recvfrom (net/socket.c:2291 (discriminator 1) net/socket.c:2287 (discriminator 1) net/socket.c:2287 (discriminator 1)) do_syscall_64 (arch/x86/entry/syscall_64.c:63 (discriminator 1) arch/x86/entry/syscall_64.c:94 (discriminator 1)) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) RIP: 0033:0x7f8911fcea06 Code: 5d e8 41 8b 93 08 03 00 00 59 5e 48 83 f8 fc 75 19 83 e2 39 83 fa 08 75 11 e8 26 ff ff ff 66 0f 1f 44 00 00 48 8b 45 10 0f 05 <48> 8b 5d f8 c9 c3 0f 1f 40 00 f3 0f 1e fa 55 48 89 e5 48 83 ec 08 RSP: 002b:00007fffdb0dccb0 EFLAGS: 00000202 ORIG_RAX: 000000000000002d RAX: ffffffffffffffda RBX: 00007fffdb0dcdc8 RCX: 00007f8911fcea06 RDX: 0000000000000001 RSI: 00007f8911a5e060 RDI: 0000000000000006 RBP: 00007fffdb0dccd0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000202 R12: 00007f89119a7d20 R13: ffffffffc4653600 R14: 0000000000000000 R15: 0000000000000000
Allocated by task 315: kasan_save_stack (mm/kasan/common.c:48) kasan_save_track (mm/kasan/common.c:60 (discriminator 1) mm/kasan/common.c:69 (discriminator 1)) __kasan_slab_alloc (mm/kasan/common.c:348) kmem_cache_alloc_ ---truncated---
{
"affected": [],
"aliases": [
"CVE-2025-38236"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-07-08T08:15:20Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\naf_unix: Don\u0027t leave consecutive consumed OOB skbs.\n\nJann Horn reported a use-after-free in unix_stream_read_generic().\n\nThe following sequences reproduce the issue:\n\n $ python3\n from socket import *\n s1, s2 = socketpair(AF_UNIX, SOCK_STREAM)\n s1.send(b\u0027x\u0027, MSG_OOB)\n s2.recv(1, MSG_OOB) # leave a consumed OOB skb\n s1.send(b\u0027y\u0027, MSG_OOB)\n s2.recv(1, MSG_OOB) # leave a consumed OOB skb\n s1.send(b\u0027z\u0027, MSG_OOB)\n s2.recv(1) # recv \u0027z\u0027 illegally\n s2.recv(1, MSG_OOB) # access \u0027z\u0027 skb (use-after-free)\n\nEven though a user reads OOB data, the skb holding the data stays on\nthe recv queue to mark the OOB boundary and break the next recv().\n\nAfter the last send() in the scenario above, the sk2\u0027s recv queue has\n2 leading consumed OOB skbs and 1 real OOB skb.\n\nThen, the following happens during the next recv() without MSG_OOB\n\n 1. unix_stream_read_generic() peeks the first consumed OOB skb\n 2. manage_oob() returns the next consumed OOB skb\n 3. unix_stream_read_generic() fetches the next not-yet-consumed OOB skb\n 4. unix_stream_read_generic() reads and frees the OOB skb\n\n, and the last recv(MSG_OOB) triggers KASAN splat.\n\nThe 3. above occurs because of the SO_PEEK_OFF code, which does not\nexpect unix_skb_len(skb) to be 0, but this is true for such consumed\nOOB skbs.\n\n while (skip \u003e= unix_skb_len(skb)) {\n skip -= unix_skb_len(skb);\n skb = skb_peek_next(skb, \u0026sk-\u003esk_receive_queue);\n ...\n }\n\nIn addition to this use-after-free, there is another issue that\nioctl(SIOCATMARK) does not function properly with consecutive consumed\nOOB skbs.\n\nSo, nothing good comes out of such a situation.\n\nInstead of complicating manage_oob(), ioctl() handling, and the next\nECONNRESET fix by introducing a loop for consecutive consumed OOB skbs,\nlet\u0027s not leave such consecutive OOB unnecessarily.\n\nNow, while receiving an OOB skb in unix_stream_recv_urg(), if its\nprevious skb is a consumed OOB skb, it is freed.\n\n[0]:\nBUG: KASAN: slab-use-after-free in unix_stream_read_actor (net/unix/af_unix.c:3027)\nRead of size 4 at addr ffff888106ef2904 by task python3/315\n\nCPU: 2 UID: 0 PID: 315 Comm: python3 Not tainted 6.16.0-rc1-00407-gec315832f6f9 #8 PREEMPT(voluntary)\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-4.fc42 04/01/2014\nCall Trace:\n \u003cTASK\u003e\n dump_stack_lvl (lib/dump_stack.c:122)\n print_report (mm/kasan/report.c:409 mm/kasan/report.c:521)\n kasan_report (mm/kasan/report.c:636)\n unix_stream_read_actor (net/unix/af_unix.c:3027)\n unix_stream_read_generic (net/unix/af_unix.c:2708 net/unix/af_unix.c:2847)\n unix_stream_recvmsg (net/unix/af_unix.c:3048)\n sock_recvmsg (net/socket.c:1063 (discriminator 20) net/socket.c:1085 (discriminator 20))\n __sys_recvfrom (net/socket.c:2278)\n __x64_sys_recvfrom (net/socket.c:2291 (discriminator 1) net/socket.c:2287 (discriminator 1) net/socket.c:2287 (discriminator 1))\n do_syscall_64 (arch/x86/entry/syscall_64.c:63 (discriminator 1) arch/x86/entry/syscall_64.c:94 (discriminator 1))\n entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)\nRIP: 0033:0x7f8911fcea06\nCode: 5d e8 41 8b 93 08 03 00 00 59 5e 48 83 f8 fc 75 19 83 e2 39 83 fa 08 75 11 e8 26 ff ff ff 66 0f 1f 44 00 00 48 8b 45 10 0f 05 \u003c48\u003e 8b 5d f8 c9 c3 0f 1f 40 00 f3 0f 1e fa 55 48 89 e5 48 83 ec 08\nRSP: 002b:00007fffdb0dccb0 EFLAGS: 00000202 ORIG_RAX: 000000000000002d\nRAX: ffffffffffffffda RBX: 00007fffdb0dcdc8 RCX: 00007f8911fcea06\nRDX: 0000000000000001 RSI: 00007f8911a5e060 RDI: 0000000000000006\nRBP: 00007fffdb0dccd0 R08: 0000000000000000 R09: 0000000000000000\nR10: 0000000000000001 R11: 0000000000000202 R12: 00007f89119a7d20\nR13: ffffffffc4653600 R14: 0000000000000000 R15: 0000000000000000\n \u003c/TASK\u003e\n\nAllocated by task 315:\n kasan_save_stack (mm/kasan/common.c:48)\n kasan_save_track (mm/kasan/common.c:60 (discriminator 1) mm/kasan/common.c:69 (discriminator 1))\n __kasan_slab_alloc (mm/kasan/common.c:348)\n kmem_cache_alloc_\n---truncated---",
"id": "GHSA-wqm2-9j5j-vxv3",
"modified": "2025-08-09T15:30:21Z",
"published": "2025-07-08T09:31:29Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-38236"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/32ca245464e1479bfea8592b9db227fdc1641705"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/61a9ad7b69ce688697e5f63332f03e17725353bc"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8db4d2d026e6e3649832bfe23b96c4acff0756db"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a12237865b48a73183df252029ff5065d73d305e"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/fad0a2c16062ac7c606b93166a7ce9d265bab976"
},
{
"type": "WEB",
"url": "https://project-zero.issues.chromium.org/issues/423023990"
}
],
"schema_version": "1.4.0",
"severity": []
}
Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
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