VulnerabilityPublished 25 Sep 2026Updated 30 Oct 2026

CVE-2026-97557: Linux kernel · smb: client: avoid leaking refcount in cifs_queue_oplock_break()

Source GCVE Database

Authoritative record:CVE-2026-97557· High 7.5

Not known to be exploited · CVSS 7.5 High · fixed in dfe7b750c7e069873a8a57a11c816831a235618a : patch Linux kernel soon.

Data as of 30 Oct 2026, 17:19 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 dfe7b750c7e069873a8a57a11c816831a235618a, de2a6bcff2659bea40c7485115b57f0ae189fc01, af0193bbf1ac8c0f67f972998b0cc629d6116cf6 +10

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 25 Sep 2026
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.

ghsa-v47h-9mpw-4682

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected >=3.16.72 <3.17 >=4.9.171 <4.10 >=4.14.114 <4.15 >=4.19.37 <4.20 >=5.0.10 <5.1	Fixed in dfe7b750c7e069873a8a57a11c816831a235618a de2a6bcff2659bea40c7485115b57f0ae189fc01 af0193bbf1ac8c0f67f972998b0cc629d6116cf6 735a3a610136ae10f381d0909dff38e5b5c5f056 13b9519b19e6e58a6cd01e63062cd1da7bd6449a 9f2e63f1b2d5fc5b5423424902c091123e220e7e 5.1 4.20 4.15 4.10 3.17 2ed2c29dd9593637cfa25ac1eb23241b20202778 0fb92ac85db58945ad7b970ff17674001487b3a3
LinuxLinux	Affected =5.1	Fixed in–

AI-suggested

A fix for this vulnerability has been implemented in the Linux kernel by adjusting the reference counting logic in cifs_queue_oplock_break() to increment the reference count only after successful queueing of the work item. Users should apply the official kernel updates that include this fix to remediate the issue.

Description

CVE-2026-97557 is a vulnerability in the Linux kernel's SMB client implementation where a reference count leak occurs in the cifs_queue_oplock_break() function. This happens because the function increments a file reference count before queueing a work item, but if the work item is not queued due to a second oplock break arriving, the reference count is never decremented. This leak can cause unmount operations for the CIFS filesystem to fail, resulting in kernel bugs related to busy inodes.

References

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