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CVE-2025-21767

Exploitation: none

CVSS base score: not scored

Vendor: Linux   Product: Linux

Description

In the Linux kernel, the following vulnerability has been resolved: clocksource: Use migrate_disable() to avoid calling get_random_u32() in atomic context The following bug report happened with a PREEMPT_RT kernel: BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48 in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 2012, name: kwatchdog preempt_count: 1, expected: 0 RCU nest depth: 0, expected: 0 get_random_u32+0x4f/0x110 clocksource_verify_choose_cpus+0xab/0x1a0 clocksource_verify_percpu.part.0+0x6b/0x330 clocksource_watchdog_kthread+0x193/0x1a0 It is due to the fact that clocksource_verify_choose_cpus() is invoked with preemption disabled. This function invokes get_random_u32() to obtain random numbers for choosing CPUs. The batched_entropy_32 local lock and/or the base_crng.lock spinlock in driver/char/random.c will be acquired during the call. In PREEMPT_RT kernel, they are both sleeping locks and so cannot be acquired in atomic context. Fix this problem by using migrate_disable() to allow smp_processor_id() to be reliably used without introducing atomic context. preempt_disable() is then called after clocksource_verify_choose_cpus() but before the clocksource measurement is being run to avoid introducing unexpected latency.

Research & News Coverage

No mentions found in monitored research blogs or news feeds.

Referenced in Advisories

DateAdvisoryIssuer
2026-10-22 ICSA-26-295-16: Siemens SIMATIC S7-1500 TM MFP CISA
2025-06-11 ICSA-25-162-05: Siemens SIMATIC S7-1500 CPU family CISA

Lifecycle Timeline

Each milestone comes from a different source, so gaps between them are gaps in what those sources publish, not evidence that nothing happened. EPSS history for this CVE holds 3 points from 2026-11-05, tracked daily from 2026-11-05; earlier points are weekly, which dates a spike to within a week. Peak probability 0.2% on 2026-11-05.

Published Applicability

Red Hat CSAF/VEX 151 affected · 0 fixed · 49 not affected
OSV.dev (incl. GHSA) 18 affected · 16 fixed · 0 not affected
CVE List v5 (CNA container) 13 affected · 0 fixed · 8 not affected
CVE List v5 (ADP/Vulnrichment) 4 affected · 0 fixed · 0 not affected

Check whether a specific version is affected →

What each source publishes about which product versions carry this vulnerability, kept as written rather than merged. Absence here means no source has published applicability data, not that nothing is affected.

Detection & Exploitation

Scan
none published
Exploit / Pen Test
none published
Network IDS/IPS
none published
Host / SIEM
none published

Blind spot. No public detection — verify by version/patch. Nothing in the monitored scanner, IDS, SIEM or offensive-tool collections references this CVE, so exposure has to be established from asset inventory and patch level rather than from a signature.

Coverage across public collections only: Nuclei and OpenVAS NVT (scan); Snort and Suricata ET Open (network); Sigma and YARA (host/SIEM); Metasploit, Exploit-DB, public GitHub repositories and NVD exploit references (exploit). Absence here means nothing public was found, not that detection is impossible.
GitHub PoC repositories are collected automatically by PoC-in-GitHub (CC0) and filtered to repositories that are still online, contain code, and are starred or at least two weeks old. They are still not vetted: some are fakes and some are malware. Treat them as evidence that code was published, not as code to run.
NVD exploit references are links NVD's analysts tag as exploits; they confirm an exploit was referenced but carry no date. This product uses data from the NVD but is not endorsed or certified by the NVD.
OpenVAS coverage derives from the Greenbone Community Feed, made available under the Open Database License (ODbL) v1.0; its individual Vulnerability Tests are licensed GNU GPL v2.

No exploit-tool sightings recorded for this CVE.

Metasploit is dated by the first commit of the module file, Exploit-DB by its publication date, and GitHub repositories by their creation date. GitHub PoC repositories are filtered (still online, contain code, starred or at least two weeks old) but not vetted: some are fakes and some are malware, so they show that code was published, not that it works or is safe to run. Evidence tiers are explained on the About page.

Distribution Status

Debian · linux bookworm 6.1.129-1 trixie 6.12.16-1 forky 6.12.16-1 sid 6.12.16-1 scope: local

Where the distribution has shipped a fix, and in which version. Green means the release has resolved it, amber that it is still open. Data from the Debian Security Tracker, used under Debian's MIT / GPLv2+ terms. Debian is upstream of several other distributions, so a fix here often precedes theirs.

CISA Assessment (Vulnrichment / SSVC)

none
no
partial
—
—
2026-11-05

Federal Remediation Window (BOD 26-04)

No
no
partial control
If the asset isRemediate withinTable 1 row
Publicly exposed 60 days 8 of 16
Not publicly exposed Fix on system upgrade 16 of 16

BOD 26-04 replaced the single KEV deadline of BOD 22-01 with four inputs: whether the asset is publicly exposed, KEV status, whether exploitation is automatable, and technical impact. Exposure belongs to each agency's asset, not to the CVE, so both outcomes are shown. Automatable and technical impact come from the CISA assessment above. Days are calendar days; for KEV entries the clock starts on the date it was added, and otherwise when the agency identifies the vulnerability on an asset. Agencies make the final exposure call asset by asset, and may set shorter timelines.

External References