VulnerabilityPublished 18 Mar 2026Updated 19 Oct 2026

CVE-2026-23248: Linux kernel · Race Condition

Affects Linux kernelSource CVE Database V5

Not known to be exploited · CVSS 7.8 High · fixed in c27dea9f50ed525facb62ef647dddc4722456e07 : patch Linux kernel soon.

Data as of 26 Oct 2026, 13:47 UTC

CVSS 3.1 base score

7.8High

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

EPSS

0.1% chance of exploitation in 30 days – higher than 2% 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 cannot reliably automate steps 1–4 of the kill chain
Technical impact: Total control over the software or total information disclosure

CISA SSVC assessment, 2026-10-16.

Patch

Available – fixed in c27dea9f50ed525facb62ef647dddc4722456e07, ac7ecb65af170a7fc193e7bd8be15dac84ec6a56, 77de62ad3de3967818c3dbe656b7336ebee461d2

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

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

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

Attack Vector: Local: The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or remotely (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., tricking a legitimate user into opening a malicious document).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
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: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to 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 18 Mar 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 Linux kernel to c27dea9f50ed525facb62ef647dddc4722456e07, ac7ecb65af170a7fc193e7bd8be15dac84ec6a56 or 77de62ad3de3967818c3dbe656b7336ebee461d2.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ b709eb872e19a19607bbb6d2975bc264d59735cf, < c27dea9f50ed525facb62ef647dddc4722456e07	Fixed in c27dea9f50ed525facb62ef647dddc4722456e07
LinuxLinux	Affected ≥ b709eb872e19a19607bbb6d2975bc264d59735cf, < ac7ecb65af170a7fc193e7bd8be15dac84ec6a56	Fixed in ac7ecb65af170a7fc193e7bd8be15dac84ec6a56
LinuxLinux	Affected ≥ b709eb872e19a19607bbb6d2975bc264d59735cf, < 77de62ad3de3967818c3dbe656b7336ebee461d2	Fixed in 77de62ad3de3967818c3dbe656b7336ebee461d2
LinuxLinux	Affected =6.14	Fixed in–

AI-suggested

A fix is available and has been applied in the Linux kernel commits identified by hashes c27dea9f50ed525facb62ef647dddc4722456e07, ac7ecb65af170a7fc193e7bd8be15dac84ec6a56, and 77de62ad3de3967818c3dbe656b7336ebee461d2. Users should update to a patched kernel version that includes these commits. No additional mitigation is required beyond applying the official fix.

Description

CVE-2026-23248 is a use-after-free vulnerability in the Linux kernel's perf subsystem caused by a race condition during mmap setup. The flaw arises when the mmap_mutex is released prematurely, allowing concurrent threads to access a partially initialized or freed ring buffer, leading to refcount errors and potential memory corruption. This issue has been fixed by extending the mutex scope to cover the entire mmap operation, ensuring atomic initialization or cleanup of the ring buffer.

Impact

Exploitation of this flaw could lead to use-after-free conditions or refcount saturation warnings in the kernel, potentially causing memory corruption, system instability, or privilege escalation. The CVSS score of 7.8 indicates high severity with impacts on confidentiality, integrity, and availability. However, no known exploits in the wild have been reported.

Summary

This vulnerability in the Linux kernel perf/core component involves a refcount bug and potential use-after-free (UAF) in the perf_mmap function. The root cause is a race condition between a failing mmap() setup and a concurrent mmap() on a dependent event. Specifically, the ring_buffer (rb) is allocated and assigned under mutex protection, but the mutex is released before map_range() is called. If map_range() fails, cleanup occurs while the mutex is not held, allowing another thread to increment the reference count on an already freed ring buffer, causing UAF or refcount saturation. The fix extends the mmap_mutex to cover map_range(), preventing concurrent access to a half-initialized or freed ring buffer.

CWE-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') (opens in a new tab)
Class weaknessLikelihood of exploit: MediumOWASP Top 10 A06:2025: Insecure Design (opens in a new tab)
The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.
Architecture and Design
In languages that support it, use synchronization primitives. Only wrap these around critical code to minimize the impact on performance.
Architecture and Design
Use thread-safe capabilities such as the data access abstraction in Spring.
Architecture and Design
Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring.
OWASP Cheat Sheets
Abuse Case (opens in a new tab)
Secure Design Principles (opens in a new tab)
OWASP ASVS 4.0.3
V1.11.2 (opens in a new tab)
Attack patterns
Leveraging Time-of-Check and Time-of-Use (TOCTOU) Race Conditions (opens in a new tab)
Leveraging Race Conditions (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, 13:22 UTC

WeaknessesCWE-362

Technical details

References

Community reviews

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