CVE-2025-40271 | fs/proc: fix uaf in proc_readdir_de()

Exp

In the Linux kernel, the following vulnerability has been resolved: fs/proc: fix uaf in proc_readdir_de() Pde is erased from subdir rbtree through rb_erase(), but not set the node to EMPTY, which may result in uaf access. We should use RB_CLEAR_NODE() set the erased node to EMPTY, then pde_subdir_next() will return NULL to avoid uaf access. We found an uaf issue while using stress-ng testing, need to run testcase getdent and tun in the same time. The steps of the issue is as follows: 1) use getdent to traverse dir /proc/pid/net/dev_snmp6/, and current pde is tun3; 2) in the [time windows] unregister netdevice tun3 and tun2, and erase them from rbtree. erase tun3 first, and then erase tun2. the pde(tun2) will be released to slab; 3) continue to getdent process, then pde_subdir_next() will return pde(tun2) which is released, it will case uaf access. CPU 0 | CPU 1 ------------------------------------------------------------------------- traverse dir /proc/pid/net/dev_snmp6/ | unregister_netdevice(tun->dev) //tun3 tun2 sys_getdents64() | iterate_dir() | proc_readdir() | proc_readdir_de() | snmp6_unregister_dev() pde_get(de); | proc_remove() read_unlock(&proc_subdir_lock); | remove_proc_subtree() | write_lock(&proc_subdir_lock); [time window] | rb_erase(&root->subdir_node, &parent->subdir); | write_unlock(&proc_subdir_lock); read_lock(&proc_subdir_lock); | next = pde_subdir_next(de); | pde_put(de); | de = next; //UAF | rbtree of dev_snmp6 | pde(tun3) / \ NULL pde(tun2)

Published: 2025-12-06 Last update: 2026-06-02 Assigner: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

Conclusion & alert: CVE-2025-40271 is rated Exploit Available (50/100): medium exploitation likelihood (EPSS 3.75%). Core evidence: 1 public exploit reference(s) are indexed (Exploit-DB). Mandatory action: Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2025-40271

EDB-ID Source Kind Published Link
52550 exploit_db edb 2026-05-04 Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2025-40271

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-03 4.66% 3.75% -0.91%
2 2026-05-16 4.04% 4.66% +0.63%
3 2026-05-05 4.04%

Full EPSS history (6 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-40271

CVSS metrics for this CVE.

No CVSS data in dataset for this CVE.

Weakness enumeration for CVE-2025-40271

GitHub Security Advisory for CVE-2025-40271

GHSA-r37x-wmxh-7hvh · Severity: unknown — In the Linux kernel, the following vulnerability has been resolved: fs/proc: fix uaf in...

OS Trackers for CVE-2025-40271

vendor priority summary link
debian not yet assigned CVE-2025-40271 not yet assigned 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-2025-40271
redhat medium https://access.redhat.com/security/cve/CVE-2025-40271
suse medium CVE-2025-40271 severity moderate: SUSE including 528 source package names (13.2-9.1:libsystemd0-254.23-1.1, 13.2-9.1:libudev1-254.23-1.1, …), 888 product×package rows across 124 product lines (Container suse/sl-micro/6.0/baremetal-os-container, Container suse/sl-micro/6.0/base-os-container, … (124 product lines)): Fixed 602, Known Affected 231, Known Not Affected 30, First Fixed 25. https://www.suse.com/security/cve/CVE-2025-40271/
ubuntu medium CVE-2025-40271 medium priority: Ubuntu including 157 source packages (linux, linux-allwinner-5.19, …), 1405 status rows across 9 suites (bionic, focal, jammy, noble, plucky, questing, trusty, upstream, xenial): DNE 1010, ignored 182, released 157, needed 50, not-affected 3, pending 3. https://ubuntu.com/security/CVE-2025-40271

Affected software / configurations for CVE-2025-40271

Vendor Product Version Raw CPE
No affected products in dataset.

References for CVE-2025-40271

cvelogic Threat Intelligence