CVE-2025-21966VulnerabilityPublished 19 May 2025Updated 27 Jun 2026

Red Hat Security Advisory: kernel security update

Affects Red HatSource GCVE Database

Mentioned vulnerabilities

CVE-2025-21993

Not known to be exploited : upgrade to 10.2 when convenient.

Data as of 25 Oct 2026, 19:02 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 9% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 10.2

Exploitation evidence

Disclosed: evidence found.
CVE published 19 May 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 2026-10-25.

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 redhat/kernel to 10.2.

Affected software

Product	Affected	Fixed in
Red Hatredhat/kernel`pkg:rpm/redhat/kernel`Other threats	Affected <10.2	Fixed in 10.2

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

AI-suggested

Red Hat has released updated kernel packages that fix these vulnerabilities. Users should apply the security update for Red Hat Enterprise Linux 10 as described in the Red Hat advisory RHSA-2025:7956 and reboot the system to activate the fixes. Patch status is confirmed as available and official. No additional mitigation steps are indicated by the vendor.

Description

The kernel packages contain the Linux kernel, the core of any Linux operating system. Security Fix(es): * kernel: dm-flakey: Fix memory corruption in optional corrupt_bio_byte feature (CVE-2025-21966) * kernel: iscsi_ibft: Fix UBSAN shift-out-of-bounds warning in ibft_attr_show_nic() (CVE-2025-21993) 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 could lead to memory corruption or undefined behavior within the kernel, potentially affecting system stability or security. The advisory does not report known exploits in the wild. The impact is rated moderate by Red Hat, indicating a security risk that warrants timely patching but is not classified as critical.

Summary

Red Hat Product Security issued an advisory (RHSA-2025:7956) for Red Hat Enterprise Linux 10 kernel packages to fix two vulnerabilities: CVE-2025-21966, a memory corruption flaw in the dm-flakey kernel module's optional corrupt_bio_byte feature, and CVE-2025-21993, a UBSAN shift-out-of-bounds warning in the iscsi_ibft kernel component. These issues are addressed by updated kernel packages that must be installed and followed by a system reboot. The advisory classifies the security impact as moderate. No CVSS scores are provided in the advisory, but the vulnerabilities relate to memory safety errors (CWE-119 and CWE-125).

CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer (opens in a new tab)
Class weaknessLikelihood of exploit: High
The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
Requirements · Language Selection
Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Operation · Build and Compilation · Environment Hardening
Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index…
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)
Attack patterns
Buffer Overflow via Environment Variables (opens in a new tab)
Overflow Buffers (opens in a new tab)
Client-side Injection-induced Buffer Overflow (opens in a new tab)
Filter Failure through Buffer Overflow (opens in a new tab)
MIME Conversion (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-125Out-of-bounds Read (opens in a new tab)
Base weaknessCWE Top 25 (2025): #8
The product reads data past the end, or before the beginning, of the intended buffer.
Implementation · Input Validation
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
Architecture and Design · Language Selection
Use a language that provides appropriate memory abstractions.
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)
Attack patterns
Overread Buffers (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, 22:09 UTC

WeaknessesCWE-119, CWE-125

Technical details

References

Community reviews

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