CVE-2026-9267 in tinydtls
Summary
by MITRE • 06/29/2026
Eclipse tinydtls before commit b3efd41ad111a4920f599f51ffa4f5e9f1e72221 contains an out-of-bounds read vulnerability in the check_server_certificate() function that allows unauthenticated attackers to trigger reads beyond valid buffer boundaries by crafting a Certificate handshake message with a specific fragment_length value. Attackers can exploit missing buffer length validation before uint24 reads, memcmp, and memcpy operations during DTLS epoch 0 on both client and server paths to cause denial of service on memory-constrained devices.
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Analysis
by VulDB Data Team • 06/29/2026
The vulnerability under discussion represents a critical out-of-bounds read condition within the Eclipse tinydtls library prior to commit b3efd41ad111a4920f599f51ffa4f5e9f1e72221. This flaw exists specifically within the check_server_certificate() function and demonstrates a fundamental failure in input validation mechanisms during DTLS certificate processing. The vulnerability stems from insufficient boundary checking when handling Certificate handshake messages, creating an exploitable condition that affects both client and server implementations within the DTLS protocol stack.
The technical implementation of this vulnerability involves a specific sequence of operations where attackers can manipulate the fragment_length field within Certificate handshake messages to trigger memory access violations. During DTLS epoch 0 processing, the code performs uint24 reads, memcmp operations, and memcpy operations without proper validation of buffer boundaries. This missing validation creates a scenario where crafted malicious input can cause the application to read data beyond allocated memory regions, resulting in undefined behavior that manifests as denial of service conditions.
The operational impact of this vulnerability extends significantly to memory-constrained devices where such out-of-bounds reads can lead to system instability and complete service disruption. In embedded systems and IoT environments where resources are limited, this vulnerability becomes particularly dangerous as it can cause crashes or restarts of critical network services. The exploitability is high for unauthenticated attackers who can simply send malformed Certificate messages without requiring any prior authentication or session establishment.
From a cybersecurity perspective, this vulnerability aligns with CWE-129 and CWE-787 categories, representing improper input validation that leads to memory safety issues. The ATT&CK framework categorizes this under privilege escalation and denial of service techniques where adversaries can leverage memory corruption vulnerabilities to disrupt system operations. The vulnerability demonstrates how seemingly minor input validation gaps can create significant security implications in cryptographic libraries used across numerous networked systems.
The recommended mitigation strategies include implementing proper buffer length validation before any uint24 reads, memcmp operations, or memcpy operations during certificate processing. Developers should ensure that all input parameters are validated against expected ranges and buffer boundaries before processing. Additionally, applying the patch from commit b3efd41ad111a4920f599f51ffa4f5e9f1e72221 or equivalent fixes provides the most effective solution. Organizations should also consider implementing input sanitization measures and runtime protections such as address sanitizers to detect similar issues in other components of their DTLS implementations.