CVE-2025-21745 | blk-cgroup: Fix class @block_class's subsystem refcount leakage

In the Linux kernel, the following vulnerability has been resolved: blk-cgroup: Fix class @block_class's subsystem refcount leakage blkcg_fill_root_iostats() iterates over @block_class's devices by class_dev_iter_(init|next)(), but does not end iterating with class_dev_iter_exit(), so causes the class's subsystem refcount leakage. Fix by ending the iterating with class_dev_iter_exit().

Published: 2025-02-27 Last update: 2026-05-12 Assigner: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

Conclusion & alert: CVE-2025-21745 is rated Low Risk (23.7/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.02%). Mandatory action: Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2025-21745

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-04-17 0.05% 0.02% -0.03%
2 2025-11-13 0.04% 0.05% +0.01%
3 2025-02-27 0.04%

Full EPSS history (3 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-21745

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.5 3.1 MEDIUM
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
1.8 3.6 [email protected]

Weakness enumeration for CVE-2025-21745

GitHub Security Advisory for CVE-2025-21745

GHSA-hfgc-7c7c-g6r6 · Severity: medium — In the Linux kernel, the following vulnerability has been resolved: blk-cgroup: Fix class ...

OS Trackers for CVE-2025-21745

vendor priority summary link
debian not yet assigned CVE-2025-21745 not yet assigned priority: Debian including 2 source packages (linux, linux-6.1), 6 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 6. https://security-tracker.debian.org/tracker/CVE-2025-21745
redhat medium https://access.redhat.com/security/cve/CVE-2025-21745
suse medium CVE-2025-21745 severity moderate: SUSE including 415 source package names (2.1.3-6.11:kernel-default-6.4.0-28.1, 2.1.3-6.12:kernel-default-base-6.4.0-28.1.21.6, …), 669 product×package rows across 117 product lines (Container suse/sl-micro/6.0/base-os-container, Container suse/sl-micro/6.0/kvm-os-container, … (117 product lines)): Fixed 361, Known Affected 231, Known Not Affected 77. https://www.suse.com/security/cve/CVE-2025-21745/
ubuntu medium CVE-2025-21745 medium priority: Ubuntu including 158 source packages (linux, linux-allwinner-5.19, …), 1551 status rows across 10 suites (bionic, focal, jammy, noble, oracular, plucky, questing, trusty, upstream, xenial): DNE 1145, released 168, ignored 148, not-affected 89, needed 1. https://ubuntu.com/security/CVE-2025-21745

Affected software / configurations for CVE-2025-21745

Vendor Product Version Raw CPE
linux linux_kernel >= 5.9, < 6.1.129 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 6.2, < 6.6.78 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 6.7, < 6.12.14 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
linux linux_kernel >= 6.13, < 6.13.3 cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

References for CVE-2025-21745

URL Tags
https://git.kernel.org/stable/c/2ce09aabe009453d641a2ceb79e6461a2d4f3876 Patch
https://git.kernel.org/stable/c/38287f779b34dfe959b4b681e909f2d3d52b88be
https://git.kernel.org/stable/c/431b6ef2714be4d5babb802114987541a88b43b0 Patch
https://git.kernel.org/stable/c/67c7f213e052b1aa6caba4a7e25e303bc6997126 Patch
https://git.kernel.org/stable/c/993121481b5a87829f1e8163f47158b72679f309 Patch
https://git.kernel.org/stable/c/d1248436cbef1f924c04255367ff4845ccd9025e Patch
https://git.kernel.org/stable/c/ffb494f1e7a047bd7a41b13796fcfb08fe5beafb
https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html
https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html
https://cert-portal.siemens.com/productcert/html/ssa-082556.html
https://cert-portal.siemens.com/productcert/html/ssa-265688.html
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