What’s Vulnerable › Vulnerabilities

CVE-2025-34468: libcoap Stack-Based Buffer Overflow in Address Resolution DoS or Potential RCE

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.7% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-12-31 · updated 2026-09-23
• Weakness: CWE-121

Description

libcoap versions up to and including 4.3.5, prior to commit 30db3ea, contain a stack-based buffer overflow in address resolution when attacker-controlled hostname data is copied into a fixed 256-byte stack buffer without proper bounds checking. A remote attacker can trigger a crash and potentially achieve remote code execution depending on compiler options and runtime memory protections. Exploitation requires the proxy logic to be enabled (i.e., the proxy request handling code path in an application using libcoap).

Affected products

• libcoap: through 4.3.5

References

• https://github.com/obgm/libcoap/commit/30db3ea
• https://github.com/obgm/libcoap/pull/1737
• https://libcoap.net/
• https://www.vulncheck.com/advisories/libcoap-stack-based-buffer-overflow-in-address-resolution-dos-or-potential-rce

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