High 7.8Published Jan 20, 2025

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

Updated under an hour ago (Oct 27, 2026, 11:10 AM ET)

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It affects Linux and 4 other products. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Exploited in the last 30 days

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: 7.8 HIGH (v3.1, CNA)CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Weakness (CWE): Not given
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Linux
NVD analysis: Modified
Record last updated: Oct 14, 2026
First seen by InfoSec Signals: Oct 14, 2026

Affected products

Affected products

Linux Linux linux:linux (from the name)	21a091b970cdbcf3e8ff829234b51be6f9192766 builds before 6b63308c28987c6010b1180c72a6db4df6c68033; 21a091b970cdbcf3e8ff829234b51be6f9192766 builds before 8efff2aa2d95dc437ab67c5b4a9f1d3f367baa10; from 21a091b970cdbcf3e8ff829234b51be6f9192766 before a7085c3ae43b86d4b3d1b8275e6a67f14257e3b7; from 21a091b970cdbcf3e8ff829234b51be6f9192766 before c9a40292a44e78f71258b8522655bffaf5753bdb	CNA record
Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518_4_pn_dp_mfp (from the name)	from V3.1.6	CISA ADP
Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518f_4_pn_dp_mfp (from the name)	from V3.1.6	CISA ADP
Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP siemens:siplus_s7_1500_cpu_1518_4_pn_dp_mfp (from the name)	from V3.1.6	CISA ADP
linux linux_kernel linux:linux_kernel	from 6.1 before 6.1.125; from 6.2 before 6.6.72; from 6.7 before 6.12.10; 6.13; 6.13; 6.13; 6.13; 6.13; and 1 more ranges	NVD

References

References

https://git.kernel.org/stable/c/6b63308c28987c6010b1180c72a6db4df6c68033	patch
https://git.kernel.org/stable/c/8efff2aa2d95dc437ab67c5b4a9f1d3f367baa10	patch
https://git.kernel.org/stable/c/a7085c3ae43b86d4b3d1b8275e6a67f14257e3b7	patch
https://git.kernel.org/stable/c/c9a40292a44e78f71258b8522655bffaf5753bdb	patch
https://project-zero.issues.chromium.org/issues/388499293	issue-tracking, third-party-advisory
https://lists.debian.org/debian-lts-announce/2025/03/msg00001.html
https://cert-portal.siemens.com/productcert/html/ssa-019113.html
https://cert-portal.siemens.com/productcert/html/ssa-457936.html

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.