CVE-2026-57160 in pjproject
Summary
by MITRE • 09/04/2026
PJSIP is a free and open source multimedia communication library written in C. Prior to commit d6a0e7f, a buffer overflow can occur in pjsip_generic_array_hdr_print() in pjsip/src/pjsip/sip_msg.c, the function that serializes generic array headers (such as Allow, Require, Supported, and Unsupported). Under certain output-buffer boundary conditions the function can write one byte past the end of the buffer. This is reachable mainly in applications that parse and re-serialize incoming SIP requests — for example a proxy, SBC, or B2BUA — where a remote peer can influence the serialized message. The out-of-bounds write is a single fixed byte; code execution and information disclosure are not demonstrated, and in typical pool-based allocations the byte falls within allocation slack. This issue has been patched via commit d6a0e7f.
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Analysis
by VulDB Data Team • 09/05/2026
PJSIP serves as a foundational open-source multimedia communication library written in C, widely utilized for implementing Voice over IP and other real-time communication protocols. The vulnerability identified prior to commit d6a0e7f resides within the sip_msg.c module, specifically affecting the pjsip_generic_array_hdr_print function. This internal routine is responsible for serializing generic array headers commonly found in Session Initiation Protocol messages, including Allow, Require, Supported, and Unsupported fields. These headers are critical components of SIP signaling that dictate capabilities and requirements between communicating endpoints. The flaw manifests as a buffer overflow condition where the serialization logic fails to adequately account for output-buffer boundary constraints under specific circumstances.
The technical nature of this defect involves an out-of-bounds write operation that extends exactly one byte past the end of the allocated memory buffer. This behavior is triggered when applications parse incoming SIP requests and subsequently re-serialize them, a pattern typical in network infrastructure components such as proxies, Session Border Controllers, or Back-to-Back User Agents. In these scenarios, remote peers can influence the content of the serialized message by sending crafted headers that alter the length calculations performed during serialization. Although the overflow is limited to a single fixed byte and does not inherently guarantee arbitrary code execution or direct information disclosure due to typical pool-based memory allocation strategies where the overwritten byte often falls within allocation slack, it still represents a significant deviation from safe coding practices and violates fundamental memory safety principles.
From an industry standard perspective, this vulnerability aligns with CWE-120, which classifies buffer copy without checking size limits, specifically manifesting as a classic stack or heap-based buffer overflow depending on the allocation context. The attack vector is categorized under ATT&CK technique T1190, Exploit Public-Facing Application, as it leverages vulnerabilities in internet-facing services to potentially disrupt service availability or destabilize application memory state. While immediate exploitation for remote code execution may be difficult due to the single-byte nature of the overflow and modern memory protection mechanisms, such flaws can contribute to denial-of-service conditions through crashes or serve as a stepping stone in more complex attack chains if combined with other vulnerabilities like use-after-free issues that might arise from subsequent memory operations on corrupted structures.
Mitigation strategies primarily involve applying the patch provided in commit d6a0e7f, which corrects the boundary checks within the serialization logic to ensure writes remain strictly within allocated buffer limits. For organizations unable to immediately update their PJSIP dependencies, operational mitigations include implementing strict input validation and length limiting on incoming SIP headers before they are processed by vulnerable components. Additionally, deploying network-level protections such as deep packet inspection firewalls can help detect and block malformed SIP messages that attempt to trigger this overflow condition. Regular security audits of C-based communication libraries and adherence to static analysis tools capable of detecting buffer boundary violations are recommended to prevent similar issues in future development cycles.