CVE-2025-65496: libcoap Null Dereference — Fix

Description

NULL pointer dereference in coap_dtls_generate_cookie() 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_SSL_CTX() to return NULL.

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CVSS v3.1 Score

4.3

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L

Weakness Type (CWE)

CWE-476 CWE-476

Affected Products

Vendor	Product	Versions
libcoap	libcoap	All

References

Advisories & Patches

https://github.com/obgm/libcoap/pull/1750

Other References

https://github.com/obgm/libcoap/issues/1745

Frequently Asked Questions

What is CVE-2025-65496? +

NULL pointer dereference in coap_dtls_generate_cookie() 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_SSL_CTX() to return NULL. It has a CVSS v3.1 base score of 4.3 (MEDIUM).

How severe is CVE-2025-65496? +

CVE-2025-65496 has a CVSS v3.1 score of 4.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2025-65496? +

CVE-2025-65496 affects products from libcoap, specifically: libcoap. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-65496? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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CVE-2025-65496