CVE-2026-115942 in Qpid Proton
Summary
by MITRE • 10/29/2026
A misconfigured wildcard TLS certificate causes a stack read overflow.
This issue does not affect any wildcard certificate issued to the RFC9525 standard - the fix only accepts certificates that comply to this standard.
This issue affects Apache Qpid Proton C: through 0.40.0.
Users are recommended to upgrade to version 0.41.1, which fixes the issue.
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Analysis
by VulDB Data Team • 10/29/2026
A critical stack-based buffer overflow vulnerability exists within Apache Qpid Proton C versions up to and including 0.40.0, triggered by the processing of a misconfigured wildcard Transport Layer Security certificate. This flaw arises from insufficient validation logic when parsing X.509 certificates that utilize wildcard patterns in their subject alternative names or common names. When such a certificate is presented during the TLS handshake process, the library fails to correctly bound-check the input data before copying it into fixed-size stack buffers. This lack of rigorous boundary checking allows an attacker who can supply a crafted malicious certificate to write beyond the allocated memory space on the call stack, potentially overwriting adjacent variables or return addresses. The severity of this issue is compounded by its potential for remote code execution if the affected service processes untrusted certificates from external sources without additional validation layers.
The technical root cause lies in the specific handling of wildcard characters within certificate fields during the parsing phase. While many TLS implementations have hardened their parsers against malformed inputs, older versions of Qpid Proton C did not adequately sanitize or validate the length and structure of strings containing wildcards before performing memory operations. This oversight creates a classic stack read overflow scenario where data intended for one variable spills over into another, disrupting the control flow of the application. It is important to note that this vulnerability does not impact certificates issued in compliance with RFC 9525. The underlying architecture distinguishes between standard wildcard usage and non-compliant configurations, but the parser's failure to strictly enforce length limits on malformed inputs remains a significant risk vector for systems relying on older library versions.
From an operational perspective, the exploitation of this vulnerability could lead to service disruption through application crashes or, in more severe scenarios, arbitrary code execution with the privileges of the process running Qpid Proton C. If the broker or client is configured to accept certificates from untrusted parties without strict mutual authentication policies, an attacker could exploit this flaw remotely over the network. The impact extends beyond immediate availability; successful exploitation might allow for information disclosure by reading sensitive data stored on the stack adjacent to the overflowed buffer. This includes potential leakage of cryptographic keys, session tokens, or other confidential information processed during the TLS negotiation phase. Organizations using Qpid Proton C in high-security environments must treat this as a critical risk requiring immediate remediation due to its direct impact on core messaging infrastructure integrity.
Mitigation strategies primarily involve upgrading to Apache Qpid Proton C version 0.41.1 or later, which implements stricter validation rules that reject non-compliant certificates and properly bounds all memory operations during certificate parsing. For environments where an immediate upgrade is not feasible, administrators should implement network-level controls such as firewall rules or reverse proxy configurations to restrict TLS handshake initiation to trusted sources only. Additionally, enforcing mutual TLS authentication ensures that clients must present valid, pre-approved certificates, thereby preventing attackers from injecting malicious payloads via the certificate field. Regular auditing of certificate policies and ensuring compliance with RFC 9525 standards further reduces the attack surface by eliminating ambiguous or malformed wildcard entries before they reach the vulnerable parser logic.
This vulnerability aligns with Common Weakness Enumeration CWE-121, which describes a stack-based buffer overflow resulting from improper bounds checking on user-controlled input. In terms of adversary tactics, it relates to ATT&CK technique T1059, specifically command execution via exploitation of software vulnerabilities, as successful exploitation could allow an attacker to execute arbitrary commands within the context of the vulnerable application. The fix emphasizes strict adherence to established standards like RFC 9525, highlighting the importance of standardized compliance in preventing parsing-related exploits. By ensuring that only certificates conforming to these rigorous specifications are accepted, organizations can effectively neutralize this specific attack vector while maintaining robust communication security for their messaging systems.