PatchTheCVECVE-2026-29013: libcoap contains out-of-bounds read vulnerabilities in OSCORE Appendix B.2 CBOR unwrap handling where get_byte
CVE-2026-29013 is a critical-severity flaw (CVSS 9.8) affecting libcoap. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
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 read
Why this priority
- Critical severity
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Risk facts
| CVSS score | 9.8 (Critical) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 0.3% (top 78%) |
| CISA exploited list | No |
| Weakness | CWE-125 |
| Published | 2026-04-17 |
| Last modified | 2026-06-17 |
Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2026-29013?
libcoap: upgrade to 4.3.5b. Exact commands for each OS are on this page.
Is CVE-2026-29013 being exploited?
CVE-2026-29013 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2026-29013 affect?
CVE-2026-29013 affects libcoap. Severity is critical (CVSS 9.8). 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
How urgent is CVE-2026-29013?
Priority 45/100. Critical severity; Remotely exploitable, no login, no user action