CVE-2026-29013
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedlibcoap 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidencelibcoap contains an out-of-bounds read vulnerability 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. Since assert() statements are compiled out in release builds using NDEBUG, no runtime bounds validation occurs. 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 integer wraparound in allocation size computation.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data< 4.3.5bCVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify installed libcoap versionRun `dpkg -l | grep libcoap` or check your package manager for libcoap version, or run `coap-client --version` if available, or inspect the shared library with `strings /usr/lib/x86_64-linux-gnu/libcoap*.so | grep -i "^4\.[0-9]"`Affected if The installed version is below 4.3.5b (e.g., 4.3.4, 4.3.3, etc.)
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Determine if OSCORE support is compiled inCheck if the binary/application using libcoap was built with OSCORE support enabled - look for OSCORE-related compile flags in build logs, or run `nm libcoap.so | grep oscore` to see if OSCORE functions are presentAffected if OSCORE functionality is present and being used in your deployment
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Check if build is a release build without assert()Inspect the binary or library for the presence of assert symbols: `nm /usr/lib/x86_64-linux-gnu/libcoap-2.so.2 | grep assert` or check build configuration for NDEBUG defined in CFLAGSAffected if The library is built as a release build (NDEBUG defined) and assert() statements are compiled out
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Inspect vulnerable source file for bounds checkingIf you have access to source, examine src/oscore/oscore_cbor.c and look at the get_byte_inc() function - verify whether it uses assert() alone or has proper runtime bounds validation with if/return checksAffected if get_byte_inc() relies solely on assert() for bounds checking without runtime validation
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Check for OSCORE endpoint exposureReview your CoAP server/client configuration to determine if OSCORE option handling is enabled - check configuration files or running processes for OSCORE-related parametersAffected if OSCORE-protected CoAP endpoints are exposed to untrusted network traffic
You are affected if libcoap version is below 4.3.5b, OSCORE support is enabled in your build, and the library is compiled as a release build where assert() statements are disabled, allowing the vulnerable bounds-check code path to be reachable.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped4.3.5b
Replace assert()-based bounds checking with proper runtime bounds validation in get_byte_inc() and related CBOR parsing functions. Apply any vendor security patches for libcoap when available. Consider defensive measures such as fuzz testing OSCORE input paths and ensuring production builds maintain security-relevant assertions or use static analysis tools to catch missing bounds checks.
Libcoap 4.3.5b
- 1. Identify the current Libcoap version in use by checking the project dependencies or installed library version
- 2. Obtain Libcoap version 4.3.5b or later from the official GitHub repository (https://github.com/obgm/libcoap)
- 3. Replace the existing Libcoap installation with version 4.3.5b or later
- 4. Recompile the project with the new Libcoap version, ensuring NDEBUG is not defined if debug assertions are desired for development builds
- 5. Rebuild and redeploy all services and applications that depend on Libcoap
- 6. Verify that OSCORE functionality works correctly with test cases, especially CBOR parsing and OSCORE option handling
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing12.0 h
- Review / QA4.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2026-29013 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-29013 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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