CVE-2025-38236 [High] | Use-After-Free in Linux Kernel

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 1. unix_stream_read_generic() peeks the first consumed OOB skb 2. manage_oob() returns the next consumed OOB skb 3. unix_stream_read_generic() fetches the next not-yet-consumed OOB skb 4. 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: <TASK> 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 </TASK> 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---

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-06-15	0.02%	0.25%	+0.23%
2	2025-07-08	—	0.02%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-06-15

0.02%

0.25%

+0.23%

2025-07-08

—

0.02%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
7.8	3.1	HIGH	`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H` Click to expand Attack vector (AV:L) They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:L) A normal user session is enough; they don’t have to be admin. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:H) Serious risk that confidential data gets exposed in a big way. Integrity (I:H) They could widely tamper with or forge data—trust in the data is badly hurt. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	1.8	5.9	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

7.8

3.1

HIGH

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H Click to expand

Attack vector (AV:L): They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L): A normal user session is enough; they don’t have to be admin.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H): Serious risk that confidential data gets exposed in a big way.
Integrity (I:H): They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

1.8

5.9

[email protected]

OS Trackers for CVE-2025-38236

vendor	priority	summary	link
`debian`	unimportant	CVE-2025-38236 unimportant priority: Debian including 2 source packages (linux, linux-6.1), 6 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 6.	https://security-tracker.debian.org/tracker/CVE-2025-38236
`redhat`	high	—	https://access.redhat.com/security/cve/CVE-2025-38236
`suse`	high	CVE-2025-38236 severity important: SUSE including 433 source package names (2.1.3-6.67:kernel-default-base-6.4.0-32.1.21.10, 2.1.3-7.44:kernel-default-6.4.0-32.1, …), 913 product×package rows across 186 product lines (Container suse/sl-micro/6.0/base-os-container, Container suse/sl-micro/6.0/kvm-os-container, … (186 product lines)): Fixed 476, Known Affected 231, Known Not Affected 206.	https://www.suse.com/security/cve/CVE-2025-38236/
`ubuntu`	medium	CVE-2025-38236 medium priority: Ubuntu including 158 source packages (linux, linux-allwinner-5.19, …), 1551 status rows across 10 suites (bionic, focal, jammy, noble, oracular, plucky, questing, trusty, upstream, xenial): DNE 1145, released 169, ignored 164, not-affected 66, needed 3, needs-triage 2, pending 2.	https://ubuntu.com/security/CVE-2025-38236

Affected software / configurations for CVE-2025-38236

Vendor	Product	Version	Raw CPE
linux	linux_kernel	>= 5.15, < 5.15.194	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 5.16, < 6.1.143	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.2, < 6.6.96	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.7, < 6.12.36	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	>= 6.13, < 6.15.5	cpe:2.3:o:linux:linux_kernel::::::::
linux	linux_kernel	6.16	cpe:2.3:o:linux:linux_kernel:6.16:rc1::::::
linux	linux_kernel	6.16	cpe:2.3:o:linux:linux_kernel:6.16:rc2::::::
linux	linux_kernel	6.16	cpe:2.3:o:linux:linux_kernel:6.16:rc3::::::
debian	debian_linux	11.0	cpe:2.3:o:debian:debian_linux:11.0:::::::*

References for CVE-2025-38236

URL	Tags
https://git.kernel.org/stable/c/32ca245464e1479bfea8592b9db227fdc1641705	Patch
https://git.kernel.org/stable/c/523edfed4f68b7794d85b9ac828c5f8f4442e4c5	Patch
https://git.kernel.org/stable/c/61a9ad7b69ce688697e5f63332f03e17725353bc	Patch
https://git.kernel.org/stable/c/8db4d2d026e6e3649832bfe23b96c4acff0756db	Patch
https://git.kernel.org/stable/c/a12237865b48a73183df252029ff5065d73d305e	Patch
https://git.kernel.org/stable/c/fad0a2c16062ac7c606b93166a7ce9d265bab976	Patch
https://project-zero.issues.chromium.org/issues/423023990	Issue Tracking
https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html	Mailing List Third Party Advisory
https://cert-portal.siemens.com/productcert/html/ssa-082556.html

URL

CVE-2025-38236 | af_unix: Don't leave consecutive consumed OOB skbs.

Exploit prediction scoring system (EPSS) score for CVE-2025-38236

Common vulnerability scoring system (CVSS) metrics for CVE-2025-38236

Weakness enumeration for CVE-2025-38236

GitHub Security Advisory for CVE-2025-38236

OS Trackers for CVE-2025-38236

Affected software / configurations for CVE-2025-38236

References for CVE-2025-38236