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
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| 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.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | libcoap3 | 4.3.5-3 | — |
| Debian 13 | libcoap3 | 4.3.4-1.1+deb13u3 | — |
| Debian 12 | libcoap3 | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| 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)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 20.04 LTS | libcoap2 | No fix yet | — |
| Ubuntu 18.04 LTS | libcoap | No fix yet | — |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | libcoap | 4.3.5b-1.1 | openSUSE-SU-2026:10592-1 |
Advisories 1
- openSUSE-SU-2026:10592-1 libcoap-devel-4.3.5b-1.1 on GA media SUSE / openSUSE Security Updates · Apr 22, 2026