# CVE-2025-21887

## Summary

- **CVE ID:** CVE-2025-21887
- **Severity:** HIGH
- **CVSS Score:** 7.8 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)
- **CWE:** N/A
- **Published:** Mar 27, 2025
- **Last Modified:** Sep 8, 2026

## Description

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

ovl: fix UAF in ovl_dentry_update_reval by moving dput() in ovl_link_up

The issue was caused by dput(upper) being called before
ovl_dentry_update_reval(), while upper->d_flags was still
accessed in ovl_dentry_remote().

Move dput(upper) after its last use to prevent use-after-free.

BUG: KASAN: slab-use-after-free in ovl_dentry_remote fs/overlayfs/util.c:162 [inline]
BUG: KASAN: slab-use-after-free in ovl_dentry_update_reval+0xd2/0xf0 fs/overlayfs/util.c:167

Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:114
 print_address_description mm/kasan/report.c:377 [inline]
 print_report+0xc3/0x620 mm/kasan/report.c:488
 kasan_report+0xd9/0x110 mm/kasan/report.c:601
 ovl_dentry_remote fs/overlayfs/util.c:162 [inline]
 ovl_dentry_update_reval+0xd2/0xf0 fs/overlayfs/util.c:167
 ovl_link_up fs/overlayfs/copy_up.c:610 [inline]
 ovl_copy_up_one+0x2105/0x3490 fs/overlayfs/copy_up.c:1170
 ovl_copy_up_flags+0x18d/0x200 fs/overlayfs/copy_up.c:1223
 ovl_rename+0x39e/0x18c0 fs/overlayfs/dir.c:1136
 vfs_rename+0xf84/0x20a0 fs/namei.c:4893
...
 </TASK>

## Affected Products

- Linux — Linux (714ba10a6dd19752a349e59aa875f3288ccb59b9)
- Linux — Linux (62f29ca45f832e281fc14966ac25f6ff3bd121ca)
- Linux — Linux (e4f2a1feebb3f209a0fca82aa53507a5b8be4d53)
- Linux — Linux (b07d5cc93e1b28df47a72c519d09d0a836043613)
- Linux — Linux (33ab4dd6202f359558a0a2678b94d1b9994c17e5)
- Linux — Linux (1ecdc55e5cd9f70f8d7513802971d4cffb9f77af)
- Linux — Linux (6.5)
- Linux — Linux (0)
- Linux — Linux (5.10.247)
- Linux — Linux (5.15.179)
- Linux — Linux (6.1.130)
- Linux — Linux (6.6.81)
- Linux — Linux (6.12.18)
- Linux — Linux (6.13.6)
- Linux — Linux (6.14)
- Linux — Linux (5.10.188)
- Linux — Linux (5.15.121)
- Linux — Linux (6.1.39)
- Linux — Linux (6.3.13)
- Linux — Linux (6.4.4)

## References

- [CNA](https://git.kernel.org/stable/c/f77618291836168eca99e89cd175256f928f5e64)
- [CNA](https://git.kernel.org/stable/c/4b49d939b5a79117f939b77cc67efae2694d9799)
- [CNA](https://git.kernel.org/stable/c/a7c41830ffcd17b2177a95a9b99b270302090c35)
- [CNA](https://git.kernel.org/stable/c/64455c8051c3aedc71abb7ec8d47c80301f99f00)
- [CNA](https://git.kernel.org/stable/c/3594aad97e7be2557ca9fa9c931b206b604028c8)
- [CNA](https://git.kernel.org/stable/c/60b4b5c1277fc491da9e1e7abab307bfa39c2db7)
- [CNA](https://git.kernel.org/stable/c/c84e125fff2615b4d9c259e762596134eddd2f27)
- [CVE](https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html)
- [siemens-SADP](https://cert-portal.siemens.com/productcert/html/ssa-019113.html)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.21%
- **EPSS Percentile:** 11.8

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-17._