VulnerabilityPublished 18 Mar 2026Updated 19 Oct 2026

CVE-2025-71269: Linux kernel · Use After Free

Affects Linux kernelSource CVE Database V5

Not known to be exploited · CVSS 7.5 High · fixed in f8da41de0bff9eb1d774a7253da0c9f637c4470a : patch Linux kernel soon.

Data as of 26 Oct 2026, 13:47 UTC

CVSS 3.1 base score

7.5High

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

EPSS

0.2% chance of exploitation in 30 days – higher than 13% 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, 2026-10-16.

Patch

Available – fixed in f8da41de0bff9eb1d774a7253da0c9f637c4470a, 6de3a371a8b9fd095198b1aa68c22cc10a4c6961, 3edd1f6c7c520536b62b2904807033597554dbac +2

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 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 to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 94ed938aba557aa798acf496f09afb289b619fcd, < f8da41de0bff9eb1d774a7253da0c9f637c4470a	Fixed in f8da41de0bff9eb1d774a7253da0c9f637c4470a
LinuxLinux	Affected ≥ 94ed938aba557aa798acf496f09afb289b619fcd, < 6de3a371a8b9fd095198b1aa68c22cc10a4c6961	Fixed in 6de3a371a8b9fd095198b1aa68c22cc10a4c6961
LinuxLinux	Affected ≥ 94ed938aba557aa798acf496f09afb289b619fcd, < 3edd1f6c7c520536b62b2904807033597554dbac	Fixed in 3edd1f6c7c520536b62b2904807033597554dbac
LinuxLinux	Affected ≥ 94ed938aba557aa798acf496f09afb289b619fcd, < 3a9fd45afadec1fbfec72057b9473d509fa8b68c	Fixed in 3a9fd45afadec1fbfec72057b9473d509fa8b68c
LinuxLinux	Affected ≥ 94ed938aba557aa798acf496f09afb289b619fcd, < 0a1fbbd780f04d1b6cf48dd327c866ba937de1c4	Fixed in 0a1fbbd780f04d1b6cf48dd327c866ba937de1c4
LinuxLinux	Affected =4.4	Fixed in–

AI-suggested

A fix is available and has been applied in specific Linux kernel commits identified by hashes (f8da41de0bff9eb1d774a7253da0c9f637c4470a, 6de3a371a8b9fd095198b1aa68c22cc10a4c6961, 3edd1f6c7c520536b62b2904807033597554dbac, 3a9fd45afadec1fbfec72057b9473d509fa8b68c, 0a1fbbd780f04d1b6cf48dd327c866ba937de1c4). Users should update their Linux kernel to a version including these fixes to remediate the vulnerability.

Description

CVE-2025-71269 is a high-severity vulnerability in the Linux kernel's btrfs filesystem. It involves improper handling of data reservation when falling back from inline extents due to a -ENOSPC (no space) error. Specifically, reserved quota group (qgroup) data was incorrectly freed during fallback, which could lead to use-after-free conditions affecting system stability. The issue has been fixed in specific Linux kernel commits.

Impact

The vulnerability can cause a use-after-free condition in the kernel's btrfs filesystem code, potentially leading to denial of service through system crashes or instability. There is no indication of confidentiality or integrity impact, but availability is affected due to the potential for kernel crashes.

Summary

This vulnerability occurs in the btrfs filesystem code of the Linux kernel. When an attempt to create an inline extent fails due to a -ENOSPC error, the kernel falls back to the normal copy-on-write (COW) path, reserving an extent and creating an ordered extent. However, the reserved qgroup data was always freed regardless of fallback, which is incorrect because the data is still in use. The fix ensures that reserved qgroup data is only freed if the fallback does not occur (i.e., when the return value is <= 0). This resolves a use-after-free condition that could cause kernel instability or crashes.

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

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Oct 2026, 12:09 UTC

WeaknessesCWE-416

Technical details

References

Community reviews

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