Overview
CVE-2025-65501 identifies a null pointer dereference vulnerability present in OISM’s libcoap version 4.3.5. This flaw can be triggered during a DTLS handshake process when the SSL_get_app_data() function returns a NULL value. Successful exploitation of this vulnerability could lead to a denial-of-service (DoS) condition, potentially disrupting services relying on the affected libcoap library.
Technical Details
The vulnerability resides within the coap_dtls_info_callback() function in libcoap. This function is invoked as part of the DTLS handshake procedure. The issue arises when the SSL_get_app_data() function, which aims to retrieve application-specific data associated with the SSL connection, returns a NULL pointer. The coap_dtls_info_callback() function then attempts to dereference this NULL pointer, causing the application to crash. This behavior can be intentionally triggered by a malicious actor during a DTLS handshake, effectively leading to a DoS attack.
CVSS Analysis
Currently, a CVSS score is not available (N/A) for CVE-2025-65501. However, given the potential for denial-of-service, a moderate to high severity score is anticipated depending on the availability of exploits and the impact on affected systems. It is important to monitor updates from NVD and other vulnerability databases for official CVSS scores.
Possible Impact
The primary impact of exploiting CVE-2025-65501 is a denial-of-service (DoS). By sending specially crafted DTLS handshake requests, an attacker can trigger the null pointer dereference in coap_dtls_info_callback(), causing the libcoap application to crash. This could disrupt services that rely on libcoap for secure communication, rendering them unavailable. The scope of the impact depends on the criticality of the affected service and the attacker’s ability to repeatedly trigger the vulnerability.
Mitigation or Patch Steps
The recommended mitigation is to upgrade to a patched version of libcoap. A fix has been implemented in the libcoap repository. Refer to the provided references for the specific pull request addressing this vulnerability.
- Apply the Patch: Apply the patch available in the libcoap pull request #1750. This patch addresses the null pointer dereference by properly handling the case where
SSL_get_app_data()returns NULL. - Upgrade libcoap: Upgrade to a version of libcoap that includes the fix for this vulnerability. Consult the libcoap project’s release notes for details on the fixed versions.
- Workarounds (if patching is not immediately possible): While not ideal, you may be able to implement temporary workarounds to mitigate the risk. Consider implementing input validation and sanitization on DTLS handshake requests to prevent malicious data from triggering the vulnerability. However, this is a complex task and may not be fully effective. Prioritize patching or upgrading the library.
