# CVE-2025-71074: functionfs: fix the open/removal races

CVE-2025-71074 is fixed in linux on 1 platform, first by DEBIAN-CVE-2025-71074, released January 13, 2026. It is not reported as exploited. Patch Radar priority: Urgent.

- Web page: https://patchblox.com/security/cve/CVE-2025-71074
- Priority: Urgent
- CVSS: 9.8 (Critical)
- EPSS: 0.0013
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jan 13, 2026
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-71074

## Description

In the Linux kernel, the following vulnerability has been resolved:  functionfs: fix the open/removal races  ffs_epfile_open() can race with removal, ending up with file->private_data pointing to freed object.  There is a total count of opened files on functionfs (both ep0 and dynamic ones) and when it hits zero, dynamic files get removed. Unfortunately, that removal can happen while another thread is in ffs_epfile_open(), but has not incremented the count yet. In that case open will succeed, leaving us with UAF on any subsequent read() or write().  The root cause is that ffs->opened is misused; atomic_dec_and_test() vs. atomic_add_return() is not a good idea, when object remains visible all along.  To untangle that 	* serialize openers on ffs->mutex (both for ep0 and for dynamic files) 	* have dynamic ones use atomic_inc_not_zero() and fail if we had zero ->opened; in that case the file we are opening is doomed. 	* have the inodes of dynamic files marked on removal (from the callback of simple_recursive_removal()) - clear ->i_private there. 	* have open of dynamic ones verify they hadn't been already removed, along with checking that state is FFS_ACTIVE.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 13.5 (trixie) | 6.12.115-2 | [DEBIAN-CVE-2025-71074](https://patchblox.com/security/data/fix/linux/debian-cve-2025-71074.md) | Jan 13, 2026 |
| Linux | linux Debian 14 | 6.19.6-1 | [DEBIAN-CVE-2025-71074](https://patchblox.com/security/data/fix/linux/debian-cve-2025-71074.md) | Jan 13, 2026 |

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Data as of 2026-11-07T18:46:35Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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