🛡️ CVE-2025-38734 — kernel

🔴 CVSS 9.8 — Critical ✅ No Known Exploit NVD
9.8
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

net/smc: fix UAF on smcsk after smc_listen_out()

In the Linux kernel, the following vulnerability has been resolved:

net/smc: fix UAF on smcsk after smc_listen_out()

BPF CI testing report a UAF issue:

[ 16.446633] BUG: kernel NULL pointer dereference, address: 000000000000003 0

[ 16.447134] #PF: supervisor read access in kernel mod e

[ 16.447516] #PF: error_code(0x0000) - not-present pag e

[ 16.447878] PGD 0 P4D 0

[ 16.448063] Oops: Oops: 0000 [#1] PREEMPT SMP NOPT I

[ 16.448409] CPU: 0 UID: 0 PID: 9 Comm: kworker/0:1 Tainted: G OE 6.13.0-rc3-g89e8a75fda73-dirty #4 2

[ 16.449124] Tainted: [O]=OOT_MODULE, [E]=UNSIGNED_MODUL E

[ 16.449502] Hardware name: QEMU Ubuntu 24.04 PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/201 4

[ 16.450201] Workqueue: smc_hs_wq smc_listen_wor k

[ 16.450531] RIP: 0010:smc_listen_work+0xc02/0x159 0

[ 16.452158] RSP: 0018:ffffb5ab40053d98 EFLAGS: 0001024 6

[ 16.452526] RAX: 0000000000000001 RBX: 0000000000000002 RCX: 000000000000030 0

[ 16.452994] RDX: 0000000000000280 RSI: 00003513840053f0 RDI: 000000000000000 0

[ 16.453492] RBP: ffffa097808e3800 R08: ffffa09782dba1e0 R09: 000000000000000 5

[ 16.453987] R10: 0000000000000000 R11: 0000000000000000 R12: ffffa0978274640 0

[ 16.454497] R13: 0000000000000000 R14: 0000000000000000 R15: ffffa09782d4092 0

[ 16.454996] FS: 0000000000000000(0000) GS:ffffa097bbc00000(0000) knlGS:000000000000000 0

[ 16.455557] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003 3

[ 16.455961] CR2: 0000000000000030 CR3: 0000000102788004 CR4: 0000000000770ef 0

[ 16.456459] PKRU: 5555555 4

[ 16.456654] Call Trace :

[ 16.456832] <TASK >

[ 16.456989] ? __die+0x23/0x7 0

[ 16.457215] ? page_fault_oops+0x180/0x4c 0

[ 16.457508] ? __lock_acquire+0x3e6/0x249 0

[ 16.457801] ? exc_page_fault+0x68/0x20 0

[ 16.458080] ? asm_exc_page_fault+0x26/0x3 0

[ 16.458389] ? smc_listen_work+0xc02/0x159 0

[ 16.458689] ? smc_listen_work+0xc02/0x159 0

[ 16.458987] ? lock_is_held_type+0x8f/0x10 0

[ 16.459284] process_one_work+0x1ea/0x6d 0

[ 16.459570] worker_thread+0x1c3/0x38 0

[ 16.459839] ? __pfx_worker_thread+0x10/0x1 0

[ 16.460144] kthread+0xe0/0x11 0

[ 16.460372] ? __pfx_kthread+0x10/0x1 0

[ 16.460640] ret_from_fork+0x31/0x5 0

[ 16.460896] ? __pfx_kthread+0x10/0x1 0

[ 16.461166] ret_from_fork_asm+0x1a/0x3 0

[ 16.461453] </TASK >

[ 16.461616] Modules linked in: bpf_testmod(OE) [last unloaded: bpf_testmod(OE) ]

[ 16.462134] CR2: 000000000000003 0

[ 16.462380] ---[ end trace 0000000000000000 ]---

[ 16.462710] RIP: 0010:smc_listen_work+0xc02/0x1590

The direct cause of this issue is that after smc_listen_out_connected(),

newclcsock->sk may be NULL since it will releases the smcsk. Therefore,

if the application closes the socket immediately after accept,

newclcsock->sk can be NULL. A possible execution order could be as

follows:

smc_listen_work | userspace

-----------------------------------------------------------------

lock_sock(sk) |

smc_listen_out_connected() |

| \- smc_listen_out |

| | \- release_sock |

| |- sk->sk_data_ready() |

| fd = accept();

| close(fd);

| \- socket->sk = NULL;

/* newclcsock->sk is NULL now */

SMC_STAT_SERV_SUCC_INC(sock_net(newclcsock->sk))

Since smc_listen_out_connected() will not fail, simply swapping the order

of the code can easily fix this issue.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality high, integrity high, availability high.

Affected software

CVE-2025-38734 is recorded against 2 packages.

  • kernel (from 6.13.0 up to 6.16.4)
  • linux-kernel

Timeline and source

Published on 5 September 2025 and last revised on 12 August 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

git.kernel.org (Web)
git.kernel.org (Web)
git.kernel.org (Web)
git.kernel.org (Web)
github.com (Advisory)
nvd.nist.gov (Advisory)
git.kernel.org (Package)

CVE-2025-38734 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity Critical
CVSS Score 9.8
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CWE N/A
Public Exploit ✅ No
Source NVD
Published 2025-09-05
Updated 2026-08-20
Modified 2026-08-12

Affected Packages

Software From version Fixed in
kernel 6.13.0 6.16.4
linux-kernel — —

Similar Threats

Exploit Protection

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