CVE-2021-36213
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 · uneditedHashiCorp Consul and Consul Enterprise 1.9.0 through 1.10.0 default deny policy with a single L7 application-aware intention deny action cancels out, causing the intention to incorrectly fail open, allowing L4 traffic. Fixed in 1.9.8 and 1.10.1.
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 confidenceIn HashiCorp Consul 1.9.0-1.10.0, when a default deny policy is configured with a single L7 application-aware intention deny action, the deny action is incorrectly cancelled out due to a logic error, causing the intention to fail open instead of failing closed. This allows L4 traffic to pass through when it should be blocked at the L7 layer.
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>= 1.9.0, < 1.9.8>= 1.10.0, < 1.10.1CVSS 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
- None
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
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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Check Consul versionRun `consul version` to get the installed Consul version, or check the version from the Consul binary or container image tagAffected if Version is 1.9.0 through 1.9.7, or 1.10.0 exactly (prior to 1.10.1)
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Verify default deny policy is configuredReview Consul intention configuration files or run `consul intention list` or `consul config read` to check if a default deny policy is set. Default deny is configured via the `default_policy` setting in the proxy defaults or service mesh configuration.Affected if Default deny policy is enabled (default_policy set to 'deny')
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Identify L7 application-aware intentionsList all intentions using `consul intention list -detailed` and examine them for L7 attributes such as `http`, `http_methods`, `path_prefix`, or `header` which indicate L7 (application-layer) intentionsAffected if There exists a single L7 intention with a deny action alongside a default deny policy
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Check intention evaluation logicReview the specific combination: if you have exactly one L7 deny intention with default deny policy enabled, the vulnerability applies. Test by attempting L4 traffic that should be blocked by the L7 deny rule - it will incorrectly pass through.Affected if Default deny policy combined with exactly one L7 deny intention (the logic error causes the deny to fail open)
You are affected if running Consul 1.9.0-1.9.7 or 1.10.0 with a default deny policy and a single L7 application-aware intention set to deny, as L4 traffic will incorrectly pass instead of being blocked.
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.
From vendor data1.9.81.10.1
Upgrade Consul to version 1.9.8, 1.10.1, or later. As a temporary workaround, avoid using single L7 deny intentions with default deny policies and use explicit L4 deny rules instead.
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2021-36213 — 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-2021-36213 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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