CVE-2026-68376 in Linux
Summary
by MITRE • 08/10/2026
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.
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Analysis
by VulDB Data Team • 08/10/2026
The vulnerability resides within the Linux kernel's Stream Control Transmission Protocol implementation where a critical buffer overflow condition exists in the SCTP cookie structure handling. This flaw specifically affects the authentication mechanism of SCTP connections and represents a classic buffer management error that can lead to arbitrary code execution or denial of service conditions. The issue manifests when the system attempts to initialize SCTP associations with authentication parameters, creating a scenario where memory boundaries are violated during data copying operations.
The technical root cause involves an incorrect array size calculation within the struct sctp_cookie structure that governs how authentication HMAC algorithms are stored and processed. The auth_hmacs array is designed to hold complete SCTP_AUTH_HMAC_ALGO parameters, which consist of a parameter header structure followed by multiple HMAC identifier values. However, the implementation incorrectly adds 2 bytes to the calculation instead of properly accounting for the 4-byte struct sctp_paramhdr size. This discrepancy becomes particularly problematic when dealing with four HMAC identifiers, as the resulting parameter exceeds the allocated buffer space by exactly the amount of the miscalculated padding.
During association initialization, the sctp_association_init() function performs a memory copy operation that extends beyond the bounds of the auth_hmacs buffer, directly overwriting adjacent memory regions including the auth_chunks field. This memory corruption creates a cascading effect where invalid HMAC identifiers can be accepted by the system and subsequently processed through the sctp_auth_get_hmac() function. The out-of-bounds read condition that follows represents a critical security flaw that could potentially allow attackers to extract sensitive information from kernel memory or manipulate the authentication process to bypass security controls.
This vulnerability aligns with CWE-121, heap-based buffer overflow, and CWE-787, out-of-bounds write, while also mapping to ATT&CK technique T1059.001 for command injection through kernel memory corruption. The flaw demonstrates a classic case of insufficient bounds checking in kernel space operations where user-supplied parameters can trigger memory corruption through improper buffer sizing calculations. The impact extends beyond simple denial of service to potentially enable privilege escalation or information disclosure attacks, making it particularly concerning for systems relying on SCTP authentication mechanisms.
The fix implemented addresses the core issue by correctly calculating the array size to include the full SCTP parameter header size rather than using an erroneous offset. This correction ensures that the auth_hmacs buffer properly accommodates the complete parameter structure including both the header and all associated HMAC identifiers. The remediation follows established kernel security practices for memory management and buffer allocation, preventing the overflow condition that was previously exploitable through carefully crafted SCTP authentication parameters.
This vulnerability represents a critical gap in kernel space memory safety mechanisms where improper size calculations can lead to severe security implications. The fix demonstrates the importance of precise memory accounting in kernel code and highlights how seemingly minor calculation errors can create significant security vulnerabilities. Organizations running Linux systems with SCTP functionality should prioritize this patch deployment, as the vulnerability could be exploited by attackers to gain unauthorized access or disrupt network services through manipulation of SCTP authentication parameters.