# CVE-2026-29013: libcoap3: libcoap contains out-of-bounds read vulnerabilities in OSCORE Appendix B.2 CBOR unwrap handling where get_byte_inc()...

CVE-2026-29013 is fixed in 8 products on 1 platform, first by FEDORA-2026-0CE923A09D, released April 17, 2026. It is not reported as exploited. Patch Radar priority: Urgent.

- Web page: https://patchblox.com/security/cve/CVE-2026-29013
- Priority: Urgent
- CVSS: 9.8 (critical)
- EPSS: 0.0030
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Apr 17, 2026

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | libcoap Fedora 43 | 4.3.5b-1.fc43 | [FEDORA-2026-0CE923A09D](https://patchblox.com/security/data/fix/linux/fedora-2026-0ce923a09d.md) | Apr 17, 2026 |
| Linux | libcoap-debuginfo Fedora 43 | 4.3.5b-1.fc43 | [FEDORA-2026-0CE923A09D](https://patchblox.com/security/data/fix/linux/fedora-2026-0ce923a09d.md) | Apr 17, 2026 |
| Linux | libcoap-debugsource Fedora 43 | 4.3.5b-1.fc43 | [FEDORA-2026-0CE923A09D](https://patchblox.com/security/data/fix/linux/fedora-2026-0ce923a09d.md) | Apr 17, 2026 |
| Linux | libcoap-devel Fedora 43 | 4.3.5b-1.fc43 | [FEDORA-2026-0CE923A09D](https://patchblox.com/security/data/fix/linux/fedora-2026-0ce923a09d.md) | Apr 17, 2026 |
| Linux | libcoap-doc Fedora 43 | 4.3.5b-1.fc43 | [FEDORA-2026-0CE923A09D](https://patchblox.com/security/data/fix/linux/fedora-2026-0ce923a09d.md) | Apr 17, 2026 |
| Linux | libcoap-utils Fedora 43 | 4.3.5b-1.fc43 | [FEDORA-2026-0CE923A09D](https://patchblox.com/security/data/fix/linux/fedora-2026-0ce923a09d.md) | Apr 17, 2026 |
| Linux | libcoap-utils-debuginfo Fedora 43 | 4.3.5b-1.fc43 | [FEDORA-2026-0CE923A09D](https://patchblox.com/security/data/fix/linux/fedora-2026-0ce923a09d.md) | Apr 17, 2026 |
| Linux | libcoap3 Debian 13.5 (trixie) | 4.3.4-1.1+deb13u3 | [DEBIAN-CVE-2026-29013](https://patchblox.com/security/data/fix/linux/debian-cve-2026-29013.md) | May 15, 2026 |
| Linux | libcoap3 Debian 14 | 4.3.5-3 | [DEBIAN-CVE-2026-29013](https://patchblox.com/security/data/fix/linux/debian-cve-2026-29013.md) | May 15, 2026 |

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Data as of 2026-11-08T06:59:42Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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