CVE-2025-40271

medium

Published 2026-02-09 · Modified 2026-06-02

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CVSS v3

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CVSS v4 NEW

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not yet in upstream

VIR risk

6.5

Description

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)

Predictions

Exploit likelihood

55%

Patch ETA

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Heuristic predictions, AS-IS, for prioritization only.

Mitigations

No mitigations published for this CVE yet.

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Exploits

Public proof-of-concept code below. AS-IS, for defenders and authorised testing only.

Exploit-DB

EDB-52550 local linux

aviralyash27 · 2026-05-04

Linux Kernel proc_readdir_de() 6.18-rc5 - Local Privilege Escalation

Source code queued for fetch — refresh in a moment.

OS impact

SUSE Affected 1 release

Version	Status	Fixed in
—	Affected	—

AlmaLinux Fixed 1 release

Version	Status	Fixed in
9	Fixed	`kernel-64k-devel-5.14.0-611.30.1.el9_7.aarch64.rpm`

Debian Fixed 5 releases

Version	Status	Fixed in
trixie	Fixed	`6.12.63-1`
sid	Fixed	`6.17.9-1`
forky	Fixed	`6.17.9-1`
bullseye	Fixed	`5.10.247-1`
bookworm	Fixed	`6.1.159-1`

Red Hat Fixed 2 releases

Version	Status	Fixed in
9	Fixed	—
8	Fixed	—

Rocky Linux Fixed 2 releases

Version	Status	Fixed in
9	Fixed	—
8	Fixed	—

References

Community-verified mitigations for this CVE will appear above when contributors publish them.

Verify integrity in audit chain (admin only). AS-IS.