CVE-2023-35862 in libcoap
Summary
by MITRE • 06/19/2023
libcoap 4.3.1 contains a buffer over-read via the function coap_parse_oscore_conf_mem at coap_oscore.c.
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Analysis
by VulDB Data Team • 01/11/2026
The vulnerability identified as CVE-2023-35862 affects libcoap version 4.3.1 and represents a critical buffer over-read condition within the coap_parse_oscore_conf_mem function located in the coap_oscore.c source file. This flaw manifests when processing OSCORE (Opaque Secure COAP for Constrained RESTful Environments) configuration data, which is a security protocol designed to provide end-to-end encryption and authentication for constrained network environments. The issue arises from insufficient bounds checking during the parsing of OSCORE configuration parameters, creating a scenario where maliciously crafted input can cause the application to read memory beyond the allocated buffer boundaries.
The technical implementation of this vulnerability stems from improper input validation within the OSCORE configuration parsing logic. When the coap_parse_oscore_conf_mem function processes incoming configuration data, it fails to adequately verify the length of expected data structures before attempting to read from memory locations. This buffer over-read condition can lead to information disclosure, application instability, or potentially remote code execution depending on the specific memory layout and exploitation circumstances. The vulnerability aligns with CWE-125, which describes out-of-bounds read conditions, and represents a significant concern for IoT devices and constrained environments that rely heavily on libcoap for COAP communication. The flaw is particularly dangerous in operational contexts where devices may be exposed to untrusted network traffic or where OSCORE is used for securing sensitive communications.
From an operational impact perspective, this vulnerability affects any system utilizing libcoap 4.3.1 with OSCORE functionality enabled, which includes numerous IoT platforms, smart grid implementations, and constrained device networks. The vulnerability can be exploited through malformed OSCORE configuration messages sent to devices that process such data, potentially leading to denial of service conditions, information leakage, or unauthorized access to sensitive operational data. Attackers leveraging this vulnerability could gain insights into system memory contents, which might reveal sensitive information such as cryptographic keys, internal system states, or other confidential data. The attack surface is particularly wide given that many IoT deployments use COAP with OSCORE for secure communications, making this vulnerability relevant across multiple industry sectors including industrial control systems, smart cities, and connected healthcare devices.
The recommended mitigation strategies include immediate upgrade to libcoap version 4.3.2 or later, which contains the necessary patches to address the buffer over-read condition. Organizations should also implement network segmentation and access controls to limit exposure to potentially malicious OSCORE configuration data. Additionally, deploying intrusion detection systems that can identify anomalous OSCORE configuration traffic patterns may provide early warning of exploitation attempts. Security teams should conduct thorough vulnerability assessments of all systems using libcoap, particularly those handling sensitive data or operating in untrusted network environments. The remediation process should include comprehensive testing to ensure that the patched version maintains expected functionality while eliminating the buffer over-read vulnerability. Organizations utilizing custom configurations or modified versions of libcoap should verify that their implementations also address this specific flaw through appropriate input validation mechanisms. The vulnerability demonstrates the critical importance of robust input validation in security-critical libraries and highlights the potential impact of seemingly minor implementation flaws in widely-deployed network protocols.