# CVE-2026-29013: libcoap Out-of-Bounds Read in OSCORE CBOR Unwrap Handling

> Attackers can trigger out-of-bounds reads in libcoap via crafted CoAP requests, potentially causing crashes or information disclosure.

- **Severity:** High 8.8 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 17 Apr 2026
- **Updated:** 14 Jul 2026
- **Also known as:** DEBIAN-CVE-2026-29013, GHSA-4vrr-6f8v-98rf, UBUNTU-CVE-2026-29013, openSUSE-SU-2026:10592-1

## What is CVE-2026-29013?

CVE-2026-29013 is a high-severity memory corruption vulnerability in libcoap, published on 17 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### 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.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-29013?

It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `libcoap` | openSUSE:Tumbleweed | All versions | 4.3.5b-1.1 |

Products: Libcoap Libcoap.

## How do I fix CVE-2026-29013?

Apply the vendor's patch.

## Is CVE-2026-29013 being exploited?

There is no known exploitation of CVE-2026-29013 in the wild and no public exploit code.

## Other vulnerabilities in libcoap

- [CVE-2025-34468](https://insights.sbomify.com/CVE-2025-34468/): libcoap Stack-Based Buffer Overflow in Address Resolution DoS or Potential RCE (high 8.2)
- [CVE-2025-65493](https://insights.sbomify.com/CVE-2025-65493/): Null dereference in n/a (high 7.5)
- [CVE-2025-65494](https://insights.sbomify.com/CVE-2025-65494/): Null dereference in n/a (high 7.5)
- [CVE-2025-65495](https://insights.sbomify.com/CVE-2025-65495/): Integer overflow in n/a (high 7.5)
- [CVE-2023-30362](https://insights.sbomify.com/CVE-2023-30362/): Information disclosure in n/a (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-29013 and fix it if it is affected.

What it is: CVE-2026-29013 is a high-severity memory corruption vulnerability in libcoap, published on 17 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-29013 in the wild and no public exploit code.

Affected product: libcoap. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-29013/ (Markdown: https://insights.sbomify.com/CVE-2026-29013/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-29013
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-29013
- OSV: https://osv.dev/vulnerability/CVE-2026-29013

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-29013/
Summaries are generated and may contain mistakes; the official description above is the record.