CVE-2025-21764VulnerabilityPublished 24 Jun 2025Updated 27 Jun 2026

Red Hat Security Advisory: kernel security update

Affects Red Hat kernel-rtSource GCVE Database

Not known to be exploited : upgrade the Red Hat redhat/kernel-rt package to 9.2 when convenient.

Data as of 26 Oct 2026, 08:30 UTC

Severity

Medium

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

EPSS: 0.2% chance of exploitation in 30 days – higher than 19% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 9.2

Exploitation evidence

Disclosed: evidence found.
CVE published 24 Jun 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 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 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 the Red Hat redhat/kernel-rt package to 9.2.

Affected software

Product	Affected	Fixed in
Red Hatredhat/kernel-rt`pkg:rpm/redhat/kernel-rt`Other threats	Affected <9.2	Fixed in 9.2

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A security update is available from Red Hat (RHSA-2025:9492) that fixes this vulnerability. Users of affected Red Hat Enterprise Linux 9.2 kernel-rt packages should apply the update promptly and reboot their systems to ensure the fix is applied. Refer to Red Hat's official update instructions at https://access.redhat.com/articles/11258 for detailed guidance.

Description

The kernel packages contain the Linux kernel, the core of any Linux operating system. Security Fix(es): * kernel: ndisc: use RCU protection in ndisc_alloc_skb() (CVE-2025-21764) 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 vulnerability could lead to use-after-free conditions in the kernel-rt networking code, potentially causing system instability or other unintended behavior. Red Hat rates the impact as moderate. No known exploits are reported in the wild at this time.

Summary

CVE-2025-21764 is a vulnerability in the kernel-rt packages of Red Hat Enterprise Linux 9.2, involving the use of RCU (Read-Copy-Update) protection in the ndisc_alloc_skb() function. The issue was fixed by adding RCU protection to prevent potential use-after-free conditions (CWE-416). Red Hat has released a security update (RHSA-2025:9492) that addresses this vulnerability. The update applies to Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions and Extended Life Cycle versions. The update must be installed and the system rebooted to apply the fix.

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).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 25 Jun 2026, 22:05 UTC

WeaknessesCWE-416

Technical details

References

Community reviews

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