CVE-2025-39843VulnerabilityPublished 22 Dec 2025Updated 28 Jun 2026

Red Hat Security Advisory: kernel security update

Affects Red HatSource GCVE Database

Mentioned vulnerabilities

CVE-2025-39925

Not known to be exploited.

Data as of 26 Oct 2026, 06:26 UTC

Severity

Medium

Rated by Threat Radar · No CVSS score from NVD or the CNA

EPSS: 0.1% chance of exploitation in 30 days – higher than 1% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

Exploitation evidence

Disclosed: evidence found.
CVE published 22 Dec 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-26.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Red Hatredhat/kernel`pkg:rpm/redhat/kernel`Other threats	Affected =9.6	Fixed in–

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AI-suggested

Red Hat has released updated kernel packages that address these vulnerabilities. Users should apply the security update for Red Hat Enterprise Linux 9.6 Extended Update Support as described in the Red Hat advisory RHSA-2025:23789. A system reboot is required for the update to take effect. Patch status is confirmed as available from the vendor advisory.

Description

The kernel packages contain the Linux kernel, the core of any Linux operating system. Security Fix(es): * kernel: mm: slub: avoid wake up kswapd in set_track_prepare (CVE-2025-39843) * kernel: can: j1939: implement NETDEV_UNREGISTER notification handler (CVE-2025-39925) For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Impact

The vulnerabilities affect the Linux kernel core in Red Hat Enterprise Linux 9.6 Extended Update Support. The issues could potentially impact kernel stability or functionality related to memory management and CAN networking subsystems. The advisory classifies the security impact as moderate. There are no known exploits in the wild at this time.

Summary

This advisory covers two kernel vulnerabilities in Red Hat Enterprise Linux 9.6 Extended Update Support. CVE-2025-39843 is a flaw in the kernel memory management SLUB allocator where waking up the kswapd daemon in set_track_prepare is avoided to fix the issue. CVE-2025-39925 addresses the lack of a NETDEV_UNREGISTER notification handler in the CAN J1939 networking subsystem. Both issues have been fixed in updated kernel packages provided by Red Hat. The advisory rates the impact as moderate and requires rebooting the system after applying the update.

CWE-833Deadlock (opens in a new tab)
Base weakness
The product contains multiple threads or executable segments that are waiting for each other to release a necessary lock, resulting in deadlock.
Attack patterns
Forced Deadlock (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-911Improper Update of Reference Count (opens in a new tab)
Base weaknessLikelihood of exploit: Medium
The product uses a reference count to manage a resource, but it does not update or incorrectly updates the reference count.

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 25 Jun 2026, 22:17 UTC

WeaknessesCWE-833, CWE-911

Technical details

References

Community reviews

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