Bug 2513253 (CVE-2026-68376)

Summary: CVE-2026-68376 kernel: sctp: fix auth_hmacs array size in struct sctp_cookie
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's Stream Control Transmission Protocol (SCTP) implementation. An incorrect array size calculation for the `auth_hmacs` field within the `sctp_cookie` structure could lead to a buffer overflow. During the initialization of an SCTP association, if four HMAC identifiers are configured, the system attempts to copy data beyond the allocated buffer. This results in the corruption of an adjacent memory field (`auth_chunks`) and can subsequently cause an out-of-bounds read when processing HMAC identifiers.
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Description OSIDB Bzimport 2026-08-10 12:27:13 UTC 
In the Linux kernel, the following vulnerability has been resolved:

sctp: fix auth_hmacs array size in struct sctp_cookie

The auth_hmacs array in struct sctp_cookie is supposed to store a complete
SCTP_AUTH_HMAC_ALGO parameter, which consists of a struct sctp_paramhdr
followed by N HMAC identifiers.

However, the array size was calculated using an extra 2 bytes instead of
sizeof(struct sctp_paramhdr), which is 4 bytes. When four HMAC identifiers
are configured, the HMAC-ALGO parameter stored in the endpoint is larger
than the auth_hmacs buffer in the cookie.

As a result, sctp_association_init() copies beyond the end of auth_hmacs
when initializing the association, corrupting the adjacent auth_chunks
field. This can lead to an invalid HMAC identifier being accepted and later
cause an out-of-bounds read in sctp_auth_get_hmac().

Fix the array size calculation by including the full SCTP parameter header
size.
Comment 6 Mauro Matteo Cascella 2026-08-21 20:52:01 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081043-CVE-2026-68376-5dfa@gregkh/T