CVE-2025-65499 Denial of service in n/a

Medium 4.3 Published 24 Nov 2025 Updated 24 Nov 2025

Remote attackers can cause a denial of service in libcoap via a crafted DTLS handshake triggering an array index error.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: A user has to click or open something
Fix: Available

What is CVE-2025-65499?

CVE-2025-65499 is a medium-severity denial of service vulnerability in n/a, published on 24 Nov 2025. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

Official description

Array index 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 DTLS handshake that triggers SSL_get_ex_data_X509_STORE_CTX_idx() to return -1.

Weakness: CWE-129

Which versions are affected by CVE-2025-65499?

It affects 1 product.

Products include Libcoap Libcoap.

How do I fix CVE-2025-65499?

Upgrade to a fixed version.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2025-65499 being exploited?

There is no known exploitation of CVE-2025-65499 in the wild and no public exploit code.

Sources

Also known as DEBIAN-CVE-2025-65499, GHSA-pcj9-7356-67r5, UBUNTU-CVE-2025-65499.