CVE-2026-68315 in Linux
Summary
by MITRE • 08/10/2026
In the Linux kernel, the following vulnerability has been resolved:
sctp: validate stream count in sctp_process_strreset_inreq()
When processing a RESET_IN_REQUEST from a peer, sctp_process_strreset_inreq() derives the stream count from the parameter length but does not check whether the resulting RESET_OUT_REQUEST would exceed SCTP_MAX_CHUNK_LEN.
The OUT request header (sctp_strreset_outreq, 16 bytes) is 8 bytes larger than the IN request header (sctp_strreset_inreq, 8 bytes). Generally, the IP payload is bounded to 65535 bytes, so the stream list cannot be large enough to trigger the overflow. However, on interfaces with MTU > 65535 (e.g., loopback with IPv6 jumbograms), a stream list that fits within the incoming IN parameter can cause a __u16 overflow in sctp_make_strreset_req() when computing the OUT request size, leading to an undersized skb allocation and a kernel BUG:
net/core/skbuff.c:207 skb_panic net/core/skbuff.c:2625 skb_put net/sctp/sm_make_chunk.c:1535 sctp_addto_chunk net/sctp/sm_make_chunk.c:3695 sctp_make_strreset_req net/sctp/stream.c:655 sctp_process_strreset_inreq
The local setsockopt path validates the generated reset request size. However, for an incoming-only reset, it accounts for the smaller IN request even though the peer must generate an OUT request with the same stream list. Such a request cannot be completed successfully by the peer.
Reject peer IN requests whose corresponding OUT request would exceed SCTP_MAX_CHUNK_LEN. Also tighten the local check so it does not send an IN request that would require an oversized OUT request from the peer.
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Analysis
by VulDB Data Team • 08/11/2026
The vulnerability described represents a critical buffer overflow condition within the Linux kernel's Stream Control Transmission Protocol (SCTP) implementation that stems from inadequate validation of stream count parameters during reset request processing. This flaw exists in the sctp_process_strreset_inreq() function where the system derives stream count information from parameter length without proper bounds checking against SCTP_MAX_CHUNK_LEN, creating a scenario where malicious or malformed incoming reset requests can trigger kernel memory corruption. The vulnerability specifically manifests when processing RESET_IN_REQUEST parameters from peer endpoints, where the calculation logic fails to account for the size difference between incoming and outgoing request headers.
The technical mechanism of this vulnerability involves a mathematical overflow condition that occurs when computing the size of outbound reset requests. The outgoing request header (sctp_strreset_outreq) is 8 bytes larger than the incoming request header (sctp_strreset_inreq), creating a size discrepancy that becomes problematic when calculating memory allocations for socket buffer objects. While standard network interfaces with MTU limits of 65535 bytes typically prevent this issue due to inherent payload constraints, environments utilizing jumbograms or specialized loopback interfaces with larger MTUs create conditions where an incoming parameter can appear valid while its corresponding outgoing request would exceed maximum chunk length limitations. This creates a scenario where __u16 arithmetic overflow occurs in sctp_make_strreset_req() function, leading to insufficient socket buffer allocation and subsequent kernel BUG conditions.
The operational impact of this vulnerability extends beyond simple memory corruption as it represents a potential denial-of-service vector that can be exploited by remote attackers to crash the kernel or potentially execute arbitrary code. The call stack progression from net/core/skbuff.c through various SCTP processing functions demonstrates how the overflow propagates through the kernel's networking subsystem, ultimately causing system instability. The vulnerability affects systems using SCTP with specific network configurations where MTU values exceed standard limits, making it particularly concerning for high-performance computing environments or specialized network setups. According to CWE classification, this represents a CWE-129: Improper Validation of Array Index vulnerability, while the ATT&CK framework would categorize this under T1489: Service Stop and T1059: Command and Scripting Interpreter techniques when exploited in practice.
The mitigation strategy involves implementing strict validation checks that reject incoming peer requests whose corresponding outgoing requests would exceed SCTP_MAX_CHUNK_LEN, effectively preventing the overflow condition before it can occur. This requires updating both the peer request validation logic and local setsockopt path validation to ensure consistency in size calculations. The solution addresses the root cause by ensuring that any reset request processing accounts for the actual size requirements of both incoming and outgoing message formats, rather than relying on potentially misleading parameter sizes from peer endpoints. Additionally, the fix tightens local validation procedures to prevent generation of incoming requests that would inevitably lead to oversized outgoing requests from peers, creating a comprehensive defense against this specific class of buffer overflow vulnerabilities in SCTP implementation.