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CVE-2025-21655— io_uring/eventfd: ensure io_eventfd_signal() defers another RCU period

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于当引用计数降至零时，会直接调用 io_eventfd_free 函数。

CVSS 7.8 · High EPSS 0.25% · P16

Possible ATT&CK Techniques 1 AI

T1068 · Exploitation for Privilege Escalation

Affected Version Matrix 10

VendorProduct Version RangeStatus
Linux Linux 21a091b970cdbcf3e8ff829234b51be6f9192766< 6b63308c28987c6010b1180c72a6db4df6c68033 affected
21a091b970cdbcf3e8ff829234b51be6f9192766< 8efff2aa2d95dc437ab67c5b4a9f1d3f367baa10 affected
21a091b970cdbcf3e8ff829234b51be6f9192766< a7085c3ae43b86d4b3d1b8275e6a67f14257e3b7 affected
21a091b970cdbcf3e8ff829234b51be6f9192766< c9a40292a44e78f71258b8522655bffaf5753bdb affected
6.1 affected
< 6.1 unaffected
6.1.125≤ 6.1.* unaffected
6.6.72≤ 6.6.* unaffected
… +2 more rows
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I. Basic Information for CVE-2025-21655

Vulnerability Information
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Vulnerability Title
io_uring/eventfd: ensure io_eventfd_signal() defers another RCU period
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于当引用计数降至零时，会直接调用 io_eventfd_free 函数。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 21a091b970cdbcf3e8ff829234b51be6f9192766 ~ 6b63308c28987c6010b1180c72a6db4df6c68033 -
Linux Linux 6.1 -

II. Public POCs for CVE-2025-21655

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III. Intelligence Information for CVE-2025-21655

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Patches & Fixes for CVE-2025-21655 (4)

Proof of Concept for CVE-2025-21655 (1)

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2025-21655

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