VulnerabilityPublished 5 Sep 2025Updated 30 Oct 2026

CVE-2025-39720: Linux kernel · ksmbd: fix refcount leak causing resource not released

Affects Linux kernelSource CVE Database V5

Not known to be exploited · CVSS 7.5 High · fixed in a1d2bab4d53368a526c97aba92671dd71814f95a : patch Linux kernel soon.

Data as of 30 Oct 2026, 12:49 UTC

CVSS 3.1 base score

7.5High

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

Thin evidence

One scorer or none

CVSS scores by source
CNA (Linux)	CVSS 3.1	7.5

Patch: Available – fixed in a1d2bab4d53368a526c97aba92671dd71814f95a, 263680d314eaaa27334f486d86c9fe7d19f50c8a, 89bb430f621124af39bb31763c4a8b504c9651e2 +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 5 Sep 2025
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 to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 0626e6641f6b467447c81dd7678a69c66f7746cf, < a1d2bab4d53368a526c97aba92671dd71814f95a	Fixed in a1d2bab4d53368a526c97aba92671dd71814f95a
LinuxLinux	Affected ≥ 0626e6641f6b467447c81dd7678a69c66f7746cf, < 263680d314eaaa27334f486d86c9fe7d19f50c8a	Fixed in 263680d314eaaa27334f486d86c9fe7d19f50c8a
LinuxLinux	Affected ≥ 0626e6641f6b467447c81dd7678a69c66f7746cf, < 89bb430f621124af39bb31763c4a8b504c9651e2	Fixed in 89bb430f621124af39bb31763c4a8b504c9651e2
LinuxLinux	Affected ≥ 0626e6641f6b467447c81dd7678a69c66f7746cf, < 36e010bb865fbaa1202fe9bcce3fd486d6db7606	Fixed in 36e010bb865fbaa1202fe9bcce3fd486d6db7606
LinuxLinux	Affected ≥ 0626e6641f6b467447c81dd7678a69c66f7746cf, < 9a7abce6e8c0e2145b346a6d4abf0d9655e9b0e8	Fixed in 9a7abce6e8c0e2145b346a6d4abf0d9655e9b0e8
LinuxLinux	Affected =5.15	Fixed in–

Description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix refcount leak causing resource not released When ksmbd_conn_releasing(opinfo->conn) returns true,the refcount was not decremented properly, causing a refcount leak that prevents the count from reaching zero and the memory from being released.

References

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