VulnerabilityPublished 23 Jan 2026Updated 19 Oct 2026

CVE-2026-22991: Linux kernel · libceph: make free_choose_arg_map() resilient to partial allocation

Affects Linux kernelSource CVE Database V5

Not known to be exploited · CVSS 7.5 High · fixed in f21c3fdb96833aac2f533506899fe38c19cf49d5 : patch Linux kernel soon.

Data as of 26 Oct 2026, 12:07 UTC

CVSS 3.1 base score

7.5High

How severe the flaw is on the 0–10 CVSS scale.

EPSS

0.4% chance of exploitation in 30 days – higher than 40% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

Exploitation: No evidence of active exploitation and no public proof of concept
Automatable: Attackers can reliably automate steps 1–4 of the kill chain
Technical impact: Limited control over the software or limited information exposure

CISA SSVC assessment, 2026-06-16.

Patch

Available – fixed in f21c3fdb96833aac2f533506899fe38c19cf49d5, ec1850f663da64842614c86b20fe734be070c2ba, e3fe30e57649c551757a02e1cad073c47e1e075e +4

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 23 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
LinuxLinux	Affected ≥ 5cf9c4a9959b6273675310d14a834ef14fbca37c, < f21c3fdb96833aac2f533506899fe38c19cf49d5	Fixed in f21c3fdb96833aac2f533506899fe38c19cf49d5
LinuxLinux	Affected ≥ 5cf9c4a9959b6273675310d14a834ef14fbca37c, < ec1850f663da64842614c86b20fe734be070c2ba	Fixed in ec1850f663da64842614c86b20fe734be070c2ba
LinuxLinux	Affected ≥ 5cf9c4a9959b6273675310d14a834ef14fbca37c, < e3fe30e57649c551757a02e1cad073c47e1e075e	Fixed in e3fe30e57649c551757a02e1cad073c47e1e075e
LinuxLinux	Affected ≥ 5cf9c4a9959b6273675310d14a834ef14fbca37c, < c4c2152a858c0ce4d2bff6ca8c1d5b0ef9f2cbdf	Fixed in c4c2152a858c0ce4d2bff6ca8c1d5b0ef9f2cbdf
LinuxLinux	Affected ≥ 5cf9c4a9959b6273675310d14a834ef14fbca37c, < 851241d3f78a5505224dc21c03d8692f530256b4	Fixed in 851241d3f78a5505224dc21c03d8692f530256b4
LinuxLinux	Affected ≥ 5cf9c4a9959b6273675310d14a834ef14fbca37c, < 8081faaf089db5280c3be820948469f7c58ef8dd	Fixed in 8081faaf089db5280c3be820948469f7c58ef8dd

AI-suggested

This vulnerability has been fixed in multiple Linux kernel commits as listed in the established facts. Users and administrators should update to a fixed kernel version that includes these patches. Since this is a kernel-level issue, applying the official kernel updates is the recommended remediation. No additional mitigations are indicated by the vendor advisory.

Description

CVE-2026-22991 is a high-severity vulnerability in the Linux kernel affecting version 4.13. It involves a NULL pointer dereference in the function free_choose_arg_map() due to improper handling of partial memory allocation failures. This flaw can cause a kernel crash (denial of service) when free_choose_arg_map() attempts to dereference a NULL pointer after a failed allocation in decode_choose_args().

Impact

Successful exploitation of this vulnerability can lead to a denial of service condition by crashing the kernel due to a NULL pointer dereference. There is no impact on confidentiality or integrity reported. The CVSS 3.1 base score is 7.5 (high), reflecting the network attack vector, low attack complexity, no privileges required, no user interaction, and impact limited to availability.

Summary

The vulnerability in the Linux kernel's libceph component arises because free_choose_arg_map() does not properly check for NULL pointers before dereferencing arg_map->args. Specifically, if decode_choose_args() fails to allocate memory for arg_map->args after setting arg_map->size to a non-zero value, free_choose_arg_map() will iterate over a NULL pointer, causing a NULL pointer dereference. The fix involves adding pointer checks in free_choose_arg_map() to handle partial allocation failures gracefully and prevent kernel crashes.

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).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Oct 2026, 12:07 UTC

WeaknessesCWE-476

Technical details

References

Community reviews

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