CVE-2025-21858VulnerabilityPublished 17 Jun 2026Updated 29 Oct 2026

Red Hat Security Advisory: kernel security update

Affects Linux kernelSource GCVE Database

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Mentioned vulnerabilities

Not known to be exploited : upgrade Linux kernel to 8.6.372.196.1 soon.

Data as of 30 Oct 2026, 20:25 UTC

Severity

High

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

EPSS: 0.2% chance of exploitation in 30 days – higher than 16% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 8.6.372.196.1

Exploitation evidence

Disclosed: evidence found.
CVE published 17 Jun 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 30 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.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), 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 Linux kernel to 8.6.372.196.1.

Affected software

Product	Affected	Fixed in
Red Hat Product Security Red Hat	Affected >=8.6 <8.6.372.196.1 Red Hat Red Hat Enterprise Linux Red Hat Enterprise Linux BaseOS AUS (v.8.6) Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.6) x86_64	Fixed in 8.6.372.196.1

AI-suggested

Red Hat has released updated kernel packages for Red Hat Enterprise Linux 8.6 that address these vulnerabilities. Users should apply the provided security update as detailed in the Red Hat advisory RHSA-2026:26570 and reboot affected systems to ensure the fixes take effect. Patch status is confirmed as official-fix by Red Hat. No additional mitigation steps are indicated beyond applying the update and rebooting.

Description

The kernel packages contain the Linux kernel, the core of any Linux operating system. Security Fix(es): * kernel: geneve: Fix use-after-free in geneve_find_dev(). (CVE-2025-21858) * kernel: mlxsw: spectrum_mr: Fix use-after-free when updating multicast route stats (CVE-2025-68800) * kernel: Linux kernel: Denial of service and memory corruption in RDMA umad (CVE-2026-23243) * kernel: netfilter: nf_tables: release flowtable after rcu grace period on error (CVE-2026-23392) * kernel: netfilter: ctnetlink: ensure safe access to master conntrack (CVE-2026-43116) * kernel: xfs: fix freemap adjustments when adding xattrs to leaf blocks (CVE-2026-43158) * kernel: Linux kernel: smb: client: reject userspace cifs.spnego descriptions (CVE-2026-46243) 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 collectively could lead to use-after-free conditions, denial of service, memory corruption, and improper access control within the Linux kernel. Such issues may cause system instability, crashes, or potential escalation of privileges depending on exploitation. The advisory rates the overall impact as important (high severity). No known exploits in the wild have been reported at the time of the advisory.

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-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).
CWE-131Incorrect Calculation of Buffer Size (opens in a new tab)
Base weaknessLikelihood of exploit: High
The product does not correctly calculate the size to be used when allocating a buffer.
Implementation
When allocating a buffer for the purpose of transforming, converting, or encoding an input, allocate enough memory to handle the largest possible encoding. For example, in a routine that converts "&" characters to "&" for HTML entity encoding, the output buffer needs to be at least 5 times as large as the input…
Implementation
Understand the programming language's underlying representation and how it interacts with numeric calculation (CWE-681). Pay close attention to byte size discrepancies, precision, signed/unsigned distinctions, truncation, conversion and casting between types, "not-a-number" calculations, and how the language handles…
Implementation · Input Validation
Perform input validation on any numeric input by ensuring that it is within the expected range. Enforce that the input meets both the minimum and maximum requirements for the expected range.
Attack patterns
Overflow Buffers (opens in a new tab)
Buffer Overflow via Parameter Expansion (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-617Reachable Assertion (opens in a new tab)
Base weakness
The product contains an assert() or similar statement that can be triggered by an attacker, which leads to an application exit or other behavior that is more severe than necessary.
Implementation
If the assertion statement is required (e.g., for security or reliability), change the invoking code to avoid the conditions that trigger the assertion.
Implementation
Consider changing the assertion to some other less "fatal" error. This might not be easy to implement, since other code may be needed to handle the error.
Implementation
Make sensitive open/close operations non-reachable from directly user-controlled data (e.g. open/close resources)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 1 Aug 2026, 22:37 UTC

WeaknessesCWE-416, CWE-825, CWE-131 +1

Technical details

References

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