VulnerabilityPublished 25 Sep 2026Updated 19 Oct 2026

CVE-2026-97523: Linux kernel · mptcp: close race between scheduler and state change

Affects Linux kernelSource CVE Database V5

Not known to be exploited · CVSS 7.5 High · fixed in d74b2e26b54a7dae1d87c1f19ae0d6db500e5e03 : patch Linux kernel soon.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 3.1 base score

7.5High

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

EPSS: 0.7% chance of exploitation in 30 days – higher than 53% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in d74b2e26b54a7dae1d87c1f19ae0d6db500e5e03, a09c87abf10a0a7e203137c75b5381aa63d9b31d, 42064de57fb83231fcc89663a94885f228a1ee53 +6

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
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 >=5.15.190 <5.15.222 >=5.19.4 <5.20	Fixed in d74b2e26b54a7dae1d87c1f19ae0d6db500e5e03 a09c87abf10a0a7e203137c75b5381aa63d9b31d 42064de57fb83231fcc89663a94885f228a1ee53 5883ae880f51edc4b1484e787473b865b6159ead 8f11430d51ff8365bc51b670bc3002b65ae4c6b7 5.20 5.15.222 4c856f3c151a2f3fa237caa651c44015916ca584 0a926b5df8efdfbac07e2fb7fafb21849a2ad9c0
LinuxLinux	Affected =6.0	Fixed in–

AI-suggested

A fix is available and has been applied in Linux kernel versions 5.15.222, 5.20, and other specified commits. Users and administrators should upgrade to these fixed versions to mitigate the vulnerability. No additional mitigation actions are specified or required.

Description

CVE-2026-97523 is a high-severity vulnerability in the Linux kernel's Multipath TCP (mptcp) scheduler. It involves a race condition between the scheduler and subflow socket state changes, which can cause data transmission failures and a divide-by-zero error due to an mss_now reset. This issue has been fixed by explicitly checking for the critical race scenario.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Oct 2026, 10:52 UTC

Technical details

References

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