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CirclApplication · Cloudflare

CVE-2023-1732

HIGH · 8.2 CVSS v3.1 Published 2023-05-10
Fix available
A fix is available. Upgrade to 1.3.3 or later.
See remediation →
91/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

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 · unedited
When sampling randomness for a shared secret, the implementation of Kyber and FrodoKEM, did not check whether crypto/rand.Read() returns an error. In rare deployment cases (error thrown by the Read() function), this could lead to a predictable shared secret. The tkn20 and blindrsa components did not check whether enough randomness was returned from the user provided randomness source. Typically the user provides crypto/rand.Reader, which in the vast majority of cases will always return the right number random bytes. In the cases where it does not, or the user provides a source that does not, the blinding for blindrsa is weak and integrity of the plaintext is not ensured in tkn20.

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 confidence

The Kyber and FrodoKEM implementations fail to check error returns from crypto/rand.Read() when sampling randomness for shared secrets, potentially leading to predictable secrets when randomness generation fails. Additionally, the tkn20 and blindrsa components don't validate that sufficient randomness bytes were returned from user-provided sources, resulting in weak blinding for blindrsa and loss of plaintext integrity for tkn20.

MitigationAdd error checking for all crypto/rand.Read() calls to ensure they succeed, and validate that randomness sources return the expected number of bytes before use in cryptographic operations.

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
CirclApplication
Affected:< 1.3.3

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
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/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 checks

Work through these to decide whether this CVE applies to you.

  1. Locate Cloudflare Circl library
    Search for the Circl library in your Go project dependencies (check go.mod for 'github.com/cloudflare/circl' or search for circl-related files in vendor directories)
    Affected if The Circl library is present in your environment
  2. Identify installed Circl version
    Run 'go list -m github.com/cloudflare/circl' or check your go.sum file for the circl version entry
    Affected if The version is lower than 1.3.3 (e.g., v1.3.2, v1.3.1, etc.)
  3. Detect Kyber or FrodoKEM usage
    Search codebase for imports of 'github.com/cloudflare/circl/kyber/...' or 'github.com/cloudflare/circl/kem/frodokem' and review code that generates shared secrets
    Affected if These components are used and Circl version is below 1.3.3
  4. Detect tkn20 or blindrsa usage
    Search for imports of 'github.com/cloudflare/circl/tkn20' or 'github.com/cloudflare/circl/tkn' and review code that provides custom randomness sources
    Affected if These components are used with user-provided random sources and Circl version is below 1.3.3

You are affected if Cloudflare Circl version is below 1.3.3 AND your code uses the Kyber, FrodoKEM, tkn20, or blindrsa components from this library.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 · scoped
Upgrade available Upgrade to 1.3.3 or later
Fixed in 1.3.3
Interim mitigation

Add error checking for all crypto/rand.Read() calls to ensure they succeed, and validate that randomness sources return the expected number of bytes before use in cryptographic operations.

Recommended fix High confidence

Circl 1.3.3

  1. Identify the current version of Circl being used in your project
  2. Update the Circl dependency to version 1.3.3 or later
  3. Run your project's dependency management tool (e.g., go get, go mod tidy) to update to the fixed version
  4. Rebuild and test your application to ensure the update does not break existing functionality
  5. Verify that crypto/rand.Read() error returns are properly handled in any custom code using Kyber, FrodoKEM, tkn20, or blindrsa components

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Circl Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2023-1732 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data