Vulnerability · Published Apr 17, 2026 · Assigned by VulnCheck
CVE-2026-29013libcoap Out-of-Bounds Read in OSCORE CBOR Unwrap Handling
High 8.8
In plain English
A high-severity out-of-bounds read in libcoap from libcoap. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 22% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
libcoap contains out-of-bounds read vulnerabilities in OSCORE Appendix B.2 CBOR unwrap handling where get_byte_inc() in src/oscore/oscore_cbor.c relies solely on assert() for bounds checking, which is removed in release builds compiled with NDEBUG. Attackers can send crafted CoAP requests with malformed OSCORE options or responses during OSCORE negotiation to trigger out-of-bounds reads during CBOR parsing and potentially cause out-of-bounds reads through integer wraparound in allocation size computation.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | libcoap3 | no fix listed | DEBIAN-CVE-2026-29013 |
| Debian:13 | libcoap3 | 4.3.4-1.1+deb13u3 | DEBIAN-CVE-2026-29013 |
| Debian:14 | libcoap3 | 4.3.5-3 | DEBIAN-CVE-2026-29013 |
| Ubuntu:22.04:LTS | libcoap2 | no fix listed | UBUNTU-CVE-2026-29013 |
| Ubuntu:22.04:LTS | libcoap3 | no fix listed | UBUNTU-CVE-2026-29013 |
| Ubuntu:24.04:LTS | libcoap3 | no fix listed | UBUNTU-CVE-2026-29013 |
| Ubuntu:25.10 | libcoap3 | no fix listed | UBUNTU-CVE-2026-29013 |
| Ubuntu:26.04:LTS | libcoap3 | no fix listed | UBUNTU-CVE-2026-29013 |
| Ubuntu:26.10 | libcoap3 | no fix listed | UBUNTU-CVE-2026-29013 |
Affected products (as reported)
Weakness: CWE-125 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:L/VA:H/SC:N/SI:N/SA:N