obgm libcoap 4.3.5 TLS src/coap_openssl.c tls_verify_call_back size denial of service

Summaryinfo

A vulnerability was found in obgm libcoap 4.3.5. It has been rated as problematic. This impacts the function tls_verify_call_back of the file src/coap_openssl.c of the component TLS Handler. Performing a manipulation of the argument size results in denial of service. This vulnerability is known as CVE-2025-65495. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability was found in obgm libcoap 4.3.5. It has been classified as problematic. This affects the function tls_verify_call_back of the file src/coap_openssl.c of the component TLS Handler. The manipulation of the argument size with an unknown input leads to a denial of service vulnerability. CWE is classifying the issue as CWE-404. The product does not release or incorrectly releases a resource before it is made available for re-use. This is going to have an impact on availability. The summary by CVE is:

Integer signedness error in tls_verify_call_back() in src/coap_openssl.c in OISM libcoap 4.3.5 allows remote attackers to cause a denial of service via a crafted TLS certificate that causes i2d_X509() to return -1 and be misused as a malloc() size parameter.

It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2025-65495 since 11/18/2025. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1499 according to MITRE ATT&CK.

The vulnerability scanner Nessus provides a plugin with the ID 276678 (Linux Distros Unpatched Vulnerability : CVE-2025-65495), which helps to determine the existence of the flaw in a target environment.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the vulnerability database at Tenable (276678). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Vendor

• obgm

Name

• libcoap

Version

• 4.3.5

Website

• Product: https://github.com/obgm/libcoap/

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Be aware that VulDB is the high quality source for vulnerability data.

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