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OpenAdvisories
High · 8.8 CVE-2026-29013 EUVD-2026-23535GHSA-4vrr-6f8v-98rf

libcoap Out-of-Bounds Read in OSCORE CBOR Unwrap Handling

Published Apr 17, 2026 · Updated Jul 14, 2026 · Assigned by VulnCheck

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 products

VendorProductAffectedFixed
libcoap libcoap < v4.3.5b v4.3.5b

Fixed in Linux distributions

Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.

ReleasePackageFixed inAdvisory
Debian 14 libcoap3 4.3.5-3 —
Debian 13 libcoap3 4.3.4-1.1+deb13u3 —
Debian 12 libcoap3 No fix yet —
ReleasePackageFixed inAdvisory
Ubuntu 26.10 libcoap3 No fix yet —
Ubuntu 26.04 LTS libcoap3 No fix yet —
Ubuntu 25.10 libcoap3 No fix yet —
Ubuntu 24.04 LTS libcoap3 No fix yet —
Ubuntu 22.04 LTS libcoap2 +1 No fix yet —
Show 2 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
Ubuntu 20.04 LTS libcoap2 No fix yet —
Ubuntu 18.04 LTS libcoap No fix yet —
ReleasePackageFixed inAdvisory
openSUSE Tumbleweed libcoap 4.3.5b-1.1 openSUSE-SU-2026:10592-1

Advisories 1

References