---
cve: "CVE-2025-21655"
severity: "HIGH"
cvss: 7.8
epss: "25%"
vendor: "Linux"
kev: false
exploited: false
published: "2025-01-20 14:15:27"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-09-12T16:31:01+02:00"
---

# CVE-2025-21655

> 7.8 HIGH · 🧪 PoC

## Beschreibung

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

io_uring/eventfd: ensure io_eventfd_signal() defers another RCU period

io_eventfd_do_signal() is invoked from an RCU callback, but when
dropping the reference to the io_ev_fd, it calls io_eventfd_free()
directly if the refcount drops to zero. This isn't correct, as any
potential freeing of the io_ev_fd should be deferred another RCU grace
period.

Just call io_eventfd_put() rather than open-code the dec-and-test and
free, which will correctly defer it another RCU grace period.

## CVSS-Vektor

```
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Lokal | good |
| AC Komplexität | Gering | bad |
| PR Privilegien | Gering | warn |
| UI Interaktion | Keine | bad |
| S Scope | Unverändert | good |
| C Vertraulichkeit | Hoch | bad |
| I Integrität | Hoch | bad |
| A Verfügbarkeit | Hoch | bad |

## Patch verfügbar (OSV)

- Kernel ≥ 6.1.125
- Kernel ≥ 6.6.72
- Kernel ≥ 6.12.10

## Referenzen

- <https://git.kernel.org/stable/c/6b63308c28987c6010b1180c72a6db4df6c68033>
- <https://git.kernel.org/stable/c/8efff2aa2d95dc437ab67c5b4a9f1d3f367baa10>
- <https://git.kernel.org/stable/c/a7085c3ae43b86d4b3d1b8275e6a67f14257e3b7>
- <https://git.kernel.org/stable/c/c9a40292a44e78f71258b8522655bffaf5753bdb>
- <https://project-zero.issues.chromium.org/issues/388499293>
- <https://lists.debian.org/debian-lts-announce/2025/03/msg00001.html>
- <https://cert-portal.siemens.com/productcert/html/ssa-019113.html>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2025-21655) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_