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WolfsslApplication

CVE-2021-44718

MEDIUM · 5.9 CVSS v3.1 Published 2022-09-02
Fix available
A fix is available. Upgrade to after 5.0.0 or later.
See remediation →
68/100
Remediation priority · Elevated
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
wolfSSL through 5.0.0 allows an attacker to cause a denial of service and infinite loop in the client component by sending crafted traffic from a Machine-in-the-Middle (MITM) position. The root cause is that the client module accepts TLS messages that normally are only sent to TLS servers.

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

wolfSSL through 5.0.0 contains a vulnerability where the TLS client incorrectly processes TLS messages intended only for servers. An attacker with MITM positioning can send specially crafted traffic to trigger an infinite loop in the client component, causing denial of service.

MitigationUpgrade wolfSSL to a version beyond 5.0.0 that addresses this vulnerability. As a defense-in-depth measure, implement network segmentation and certificate validation to reduce the likelihood of MITM attacks.

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
WolfsslApplication
Affected:<= 5.0.0

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
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

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

  1. Determine wolfSSL library version
    Run 'wolfssl -version' or check the library file version if installed as a package. If compiled from source, inspect the version defined in version.h or the --version output of any wolfSSL-linked binary.
    Affected if The installed version is 5.0.0 or any earlier version.
  2. Confirm wolfSSL client mode is in use
    Inspect application configuration or code that links wolfSSL to determine if the TLS client functionality (e.g., WOLFSSL client methods, WOLFSSL_CTX_new method with client-specific parameters) is enabled and actively used.
    Affected if The system operates as a TLS client using wolfSSL libraries.
  3. Verify network exposure to MITM risk
    Review network architecture and firewall rules to determine if the wolfSSL client can receive TLS traffic from untrusted networks. Check whether the client communicates over trusted-only network segments.
    Affected if The TLS client can receive TLS handshake messages from network paths where an attacker could perform MITM positioning.
  4. Check for TLS message handling configuration
    Review wolfSSL configuration options (such as NO_WOLFSSL_CLIENT or HAVE_IO) and runtime logs to confirm standard TLS client message processing paths are active.
    Affected if Standard TLS client message processing is enabled without custom message filtering.

You are affected if wolfSSL version 5.0.0 or earlier is installed AND the system functions as a TLS client that can receive traffic from network paths where a MITM attacker could inject malicious TLS server messages.

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 a release after 5.0.0
Interim mitigation

Upgrade wolfSSL to a version beyond 5.0.0 that addresses this vulnerability. As a defense-in-depth measure, implement network segmentation and certificate validation to reduce the likelihood of MITM attacks.

Recommended fix Moderate confidence

wolfSSL 5.1.0 or later stable release

  1. 1. Check the current wolfSSL version in use: `wolfssl --version` or check the library version linked to your application
  2. 2. Obtain the latest stable wolfSSL release from the official GitHub repository (github.com/wolfSSL/wolfssl) or wolfSSL website (www.wolfssl.com)
  3. 3. Review the release notes for versions greater than 5.0.0 to confirm the fix for CVE-2021-44718 is included
  4. 4. Download the fixed version (wolfSSL 5.1.0 or later stable release)
  5. 5. Rebuild and replace the wolfSSL library in your application environment
  6. 6. Test the application to verify normal TLS client functionality is maintained
  7. 7. Deploy the updated library to production
Caveat Review release notes for any API changes between 5.0.0 and the target upgrade version; TLS 1.3 may have new features or different default settings

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

Fix this in Wolfssl Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing4.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,080
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Scan for this in your stack

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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-2021-44718 in production — separate from our analysis above.

No notes yet

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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