Buffer overflow in Libcoap
CVE-2025-34468
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).
Vulnerability class: Buffer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.007 (53.2th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 53rd percentile — 53.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.007 · newest: 0.007 · change: +0.000
Affected products
- Libcoap — versions 0, 30db3eaa1f0464722ebea2ca2d5084aebfbd344d
Weakness classification (CWE)
References
- github.com/obgm/libcoap/pull/1737 (issue-tracking, Issue Tracking)
- github.com/obgm/libcoap/commit/30db3ea (Patch, patch)
- libcoap.net/ (Product, product)
- www.vulncheck.com/advisories/libcoap-stack-based-buffer-overflow-in-address-res… (Third Party Advisory, third-party-advisory)
Frequently asked questions
- What is CVE-2025-34468?
- CVE-2025-34468 is a critical-severity vulnerability in Libcoap, classified under Stack-based Buffer Overflow. CVSS score: 9.8/10. Published 2025-12-31.
- How severe is CVE-2025-34468?
- Critical severity. CVSS v3 base score is 9.8 out of 10.