VulnerabilityPublished 15 Aug 2026Updated 21 Oct 2026

CVE-2026-72398: Linux kernel · sctp: add INIT verification after cookie unpacking

Affects Linux kernelSource CVE Database V5

Not known to be exploited · CVSS 9.8 Critical · fixed in bca3100f550281c2f2418652338bced3b35af0e6 : patch Linux kernel as a priority.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 3.1 base score

9.8Critical

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

EPSS

0.7% chance of exploitation in 30 days – higher than 54% 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: Total control over the software or total information disclosure

CISA SSVC assessment, 2026-10-16.

Patch

Available – fixed in bca3100f550281c2f2418652338bced3b35af0e6, 81892d83cc897331510f35b30d17f8b0dc285966, 683a012b984fef4bc155e278742fbe01561e102a +2

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
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: 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: 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 15 Aug 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 ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < bca3100f550281c2f2418652338bced3b35af0e6	Fixed in bca3100f550281c2f2418652338bced3b35af0e6
LinuxLinux	Affected ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 81892d83cc897331510f35b30d17f8b0dc285966	Fixed in 81892d83cc897331510f35b30d17f8b0dc285966
LinuxLinux	Affected ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 683a012b984fef4bc155e278742fbe01561e102a	Fixed in 683a012b984fef4bc155e278742fbe01561e102a
LinuxLinux	Affected ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 414c5447fe6a200613dd46d7fdc8454622076cb1	Fixed in 414c5447fe6a200613dd46d7fdc8454622076cb1
LinuxLinux	Affected ≥ 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 062bcbf8d1f1051fdeb20b94920031b0e2cb95a2	Fixed in 062bcbf8d1f1051fdeb20b94920031b0e2cb95a2
LinuxLinux	Affected =2.6.12	Fixed in–

Description

In the Linux kernel, the following vulnerability has been resolved: sctp: add INIT verification after cookie unpacking In SCTP handshake, the INIT chunk is initially processed by the server and embedded into the cookie carried in INIT-ACK. The client then returns this cookie via COOKIE-ECHO, where the server unpacks it and reconstructs the original INIT chunk. When cookie authentication is enabled, the cookie contents are protected against tampering, so reusing the unpacked INIT without re-verification is safe. However, when cookie authentication is disabled, the reconstructed INIT can no longer be trusted. In this case, the INIT must be explicitly validated after unpacking to avoid processing potentially tampered data. Add sctp_verify_init() checks after cookie unpacking in COOKIE-ECHO processing paths (sctp_sf_do_5_1D_ce() and sctp_sf_do_5_2_4_dupcook()) when cookie_auth_enable is disabled. On failure, the new association is freed and the packet is discarded. Also tighten cookie validation in sctp_unpack_cookie() by verifying the embedded chunk type is SCTP_CID_INIT before treating it as an INIT chunk. Finally, update sctp_verify_init() to validate parameter bounds using the actual embedded INIT length instead of chunk->chunk_end, since the INIT stored in COOKIE-ECHO may not span the entire chunk buffer.

References

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