CVE-2025-39993VulnerabilityPublished 12 Jan 2026Updated 24 Sep 2026

Red Hat Security Advisory: kernel-rt security update

Affects Linux kernelSource GCVE Database

Mentioned vulnerabilities

Not known to be exploited · fixed in Red Hat package updates : patch Linux kernel soon.

Data as of 26 Oct 2026, 14:05 UTC

Severity

High

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

EPSS: 0.1% chance of exploitation in 30 days – higher than 4% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 4.15.0-1196.211~14.04.1, 4.4.0-1189.204, 4.4.0-1151.157 +2

Exploitation evidence

Disclosed: evidence found.
CVE published 12 Jan 2026
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 26 Oct 2026.

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 or the CVSS exploit maturity 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

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
Red Hat Product Security Red Hat	Affected <4.4.0-1151.157 <4.15.0-1196.211~14.04.1 <4.4.0-277.311~14.04.1 <4.4.0-277.311 <4.4.0-1189.204	Fixed in 4.4.0-1151.157 4.15.0-1196.211~14.04.1 4.4.0-277.311~14.04.1 4.4.0-277.311 4.4.0-1189.204

AI-suggested

A security update is available from Red Hat for the kernel-rt packages. Users should apply the update as per Red Hat's advisory RHSA-2026:0443 and reboot the system to ensure the fixes take effect. No additional mitigation steps are required beyond applying the official patch and rebooting.

Description

Multiple security vulnerabilities have been identified and fixed in the Red Hat kernel-rt packages, which provide the Real Time Linux Kernel for systems requiring high determinism. The fixes address race conditions, null pointer dereferences, and use-after-free issues in various kernel components including media, SCTP, and libceph. These vulnerabilities affect Red Hat Enterprise Linux 8 Real Time and related variants. A security update is available and should be applied, followed by a system reboot.

Impact

The vulnerabilities could cause system crashes or memory corruption due to race conditions, null pointer dereferences, or use-after-free bugs in kernel components. This may affect system stability and security on affected Red Hat Enterprise Linux 8 Real Time systems. No known exploits in the wild have been reported.

Summary

The kernel-rt packages for Red Hat Enterprise Linux 8 and related variants have been updated to fix three security vulnerabilities: CVE-2025-39993 (race condition in media rc subsystem with imon_disconnect()), CVE-2025-40240 (null pointer dereference in SCTP when chunk data buffer is missing), and CVE-2025-68285 (potential use-after-free in libceph's have_mon_and_osd_map()). These issues could lead to system instability or security risks. The vendor has released patches that address these flaws and recommends updating to the fixed versions and rebooting the system.

CWE-416Use After Free (opens in a new tab)
Variant weaknessLikelihood of exploit: HighCWE Top 25 (2025): #7
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.
Architecture and Design · Language Selection
Choose a language that provides automatic memory management.
Implementation · Attack Surface Reduction
When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
OWASP Cheat Sheets
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
OWASP ASVS 4.0.3
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
V5.1.3 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-476NULL Pointer Dereference (opens in a new tab)
Base weaknessLikelihood of exploit: MediumCWE Top 25 (2025): #13OWASP Top 10 A10:2025: Mishandling of Exceptional Conditions (opens in a new tab)
The product dereferences a pointer that it expects to be valid but is NULL.
Implementation
For any pointers that could have been modified or provided from a function that can return NULL, check the pointer for NULL before use. When working with a multithreaded or otherwise asynchronous environment, ensure that proper locking APIs are used to lock before the check, and unlock when it has finished.
Requirements
Select a programming language that is not susceptible to these issues.
Implementation
Check the results of all functions that return a value and verify that the value is non-null before acting upon it.
OWASP Cheat Sheets
Logging (opens in a new tab)
Error Handling (opens in a new tab)
OWASP ASVS 4.0.3
V11.1.7 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-825Expired Pointer Dereference (opens in a new tab)
Base weakness
The product dereferences a pointer that contains a location for memory that was previously valid, but is no longer valid.
Architecture and Design
Choose a language that provides automatic memory management.
Implementation
When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
OWASP Cheat Sheets
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
OWASP ASVS 4.0.3
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
V5.1.3 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 25 Sep 2026, 05:12 UTC

WeaknessesCWE-416, CWE-476, CWE-825

Technical details

References

Community reviews

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