CVE-2026-9267
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 · uneditedEclipse tinydtls before commit b3efd41ad111a4920f599f51ffa4f5e9f1e72221 contains an out-of-bounds read vulnerability in the check_server_certificate() function that allows unauthenticated attackers to trigger reads beyond valid buffer boundaries by crafting a Certificate handshake message with a specific fragment_length value. Attackers can exploit missing buffer length validation before uint24 reads, memcmp, and memcpy operations during DTLS epoch 0 on both client and server paths to cause denial of service on memory-constrained devices.
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 · moderate confidenceEclipse tinydtls before commit b3efd41 contains an out-of-bounds read vulnerability in check_server_certificate() where missing buffer length validation allows attackers to craft Certificate handshake messages with specific fragment_length values that trigger reads beyond valid buffer boundaries during DTLS epoch 0 processing, affecting both client and server paths.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS 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
- Authentication
- X
- User interaction
- None
- Scope
- X
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
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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Locate tinydtls in the environmentSearch for tinydtls source code directories, compiled libraries (libtinydtls.a, libtinydtls.so), or binaries that link against it. Check project dependencies, build systems, or firmware/components that may include tinydtls.Affected if tinydtls is present in the system or project dependencies
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Determine the installed tinydtls version or commitInspect the version by running 'git log' in the tinydtls source directory, checking for a VERSION file, examining the library symbol version, or reviewing the commit hash in the build artifacts. Compare against commit b3efd41.Affected if the version is earlier than commit b3efd41 or the commit hash cannot be verified to be b3efd41ad111a4920f599f51ffa4f5e9f1e72221 or later
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Verify if DTLS client certificate authentication is enabledReview the tinydtls configuration (dtls_config.h or build-time defines) for DTLS_CLIENT_CERTIFICATE_AUTH or similar flags that enable client certificate verification in the DTLS handshake. Check if the code calls dtls_verify_cached_cert or related certificate verification functions.Affected if DTLS client certificate authentication is enabled, as this triggers the vulnerable check_server_certificate() code path
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Confirm if the Certificate handshake is processed in DTLS epoch 0Monitor or review network traffic/logs for DTLS connections that include Certificate messages (handshake type 0x0b) during the initial handshake (epoch 0). Check if the application accepts incoming DTLS connections or initiates DTLS client connections with certificate verification.Affected if the environment processes DTLS Certificate handshake messages, which exercises the vulnerable buffer length validation code
The environment is affected if tinydtls version is before commit b3efd41 and DTLS connections with client certificate authentication are in use, allowing crafted Certificate messages to trigger out-of-bounds reads during DTLS epoch 0 processing.
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 · scopedUpgrade to tinydts version/commit b3efd41ad111a4920f599f51ffa4f5e9f1e72221 or later which includes proper buffer length validation before uint24 reads, memcmp, and memcpy operations in the Certificate handshake processing.
- 1. Identify the current version of Eclipse tinydtls in use by checking the git commit hash or version metadata
- 2. Navigate to the Eclipse tinydtls GitLab repository at gitlab.eclipse.org
- 3. Locate the specific fix commit: b3efd41ad111a4920f599f51ffa4f5e9f1e72221
- 4. Review the changes introduced in this commit to understand the vulnerability fix in the check_server_certificate() function
- 5. Apply the patch or cherry-pick the fix commit to the current codebase
- 6. Verify that the fix adds proper buffer length validation before uint24 reads, memcmp, and memcpy operations
- 7. Rebuild and test the tinydtls library to ensure the patch compiles correctly
- 8. Test DTLS Certificate handshake processing to confirm the vulnerability is mitigated
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation4.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,328.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-9267 — 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-2026-9267 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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- Version or environment caveats, and links to real fixes
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