Summary
In the Linux kernel, the following vulnerability has been resolved: net/smc: fix UAF on smcsk...
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]
[ 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]
[ 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.
Impact
Memory is accessed after it has been freed, leading to undefined behavior in native code. Typical impact: memory corruption, crash, or potential code execution.
CVE-2025-38734 has a CVSS score of 7.8 (High). The vector is requires local access, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. No fixed version is listed yet, so configuration controls and monitoring matter more in the interim.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Already deployed Kodem?
See it in your environmentNew to Kodem? Get a demo →Remediation advice
Frequently Asked Questions
- What is CVE-2025-38734? CVE-2025-38734 is a high-severity use after free vulnerability. No fixed version is listed yet. Memory is accessed after it has been freed, leading to undefined behavior in native code.
- How severe is CVE-2025-38734? CVE-2025-38734 has a CVSS score of 7.8 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Is there a fix for CVE-2025-38734? No fixed version is listed for CVE-2025-38734 yet. Monitor the advisory for updates and apply mitigations in the interim.
- Is CVE-2025-38734 exploitable, and should I be worried? Whether CVE-2025-38734 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2025-38734 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.