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WolfsslApplication

CVE-2026-5264

CRITICAL · 9.8 CVSS v3.1 Published 2026-04-09
Fix available
A fix is available. Upgrade to 5.9.1 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click Patch available

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
Heap buffer overflow in DTLS 1.3 ACK message processing. A remote attacker can send a crafted DTLS 1.3 ACK message that triggers a heap buffer overflow.

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 confidence

A heap buffer overflow vulnerability exists in DTLS 1.3 ACK message processing. A remote attacker can send a specially crafted DTLS 1.3 ACK message that overflows a heap-allocated buffer, potentially allowing remote code execution or denial of service.

MitigationApply the vendor-supplied patch for the affected TLS/DTLS library implementation. If no patch is available, consider restricting network access to DTLS 1.3 services or disabling DTLS 1.3 until a fix is available.

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:< 5.9.1

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
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 checks

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

  1. Determine WolfSSL library version
    Run 'wolfssl version' or check the library binary metadata (e.g., 'strings libwolfssl.so | grep -i version' or examine the header file version.h if available). Compare the installed version to the affected range: versions prior to 5.9.1 are vulnerable.
    Affected if The installed WolfSSL version is lower than 5.9.1.
  2. Verify DTLS 1.3 support is compiled in
    Check if DTLS 1.3 was enabled at compile time by inspecting the build configuration or headers. Look for the macro WOLFSSL_DTLS13 or HAVE_DTLS13 in the build environment (e.g., 'grep -r "DTLS13\|DTLsv1_3" .' in the include directory).
    Affected if DTLS 1.3 support (WOLFSSL_DTLS13 or HAVE_DTLS13) is defined in the build.
  3. Confirm DTLS 1.3 is in active use
    Review application configuration files or runtime settings for any DTLS 1.3 endpoints. Check process command-line arguments or configuration for DTLS 1.3 protocol selection. Inspect network listeners for DTLS 1.3 cipher suites if logging is available.
    Affected if The application is actively using or advertising DTLS 1.3 connections.
  4. Inspect DTLS ACK message handling configuration
    If source code is available, locate the DTLS ACK processing functions (typically in the DTLS handshake or message handling code). Verify the application does not have workarounds or bounds checking that may mitigate the overflow.
    Affected if ACK message processing in DTLS 1.3 code paths lacks proper bounds validation and the application uses DTLS 1.3.

You are affected if your WolfSSL installation is version 5.9.1 or lower, DTLS 1.3 support is compiled in, and DTLS 1.3 is actively used or configured in your environment.

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 5.9.1 or later
Fixed in 5.9.1
Vendor patch github.com →
Interim mitigation

Apply the vendor-supplied patch for the affected TLS/DTLS library implementation. If no patch is available, consider restricting network access to DTLS 1.3 services or disabling DTLS 1.3 until a fix is available.

Recommended fix High confidence

WolfSSL 5.9.1

  1. Obtain WolfSSL version 5.9.1 or later from the official wolfSSL repository
  2. Review the changes in GitHub pull request #10076 to understand the vulnerability fix
  3. Compile and install the new version following standard WolfSSL build procedures
  4. Restart any services or applications using the WolfSSL library
  5. Test DTLS 1.3 functionality to confirm the fix is working correctly

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

Fix this in Wolfssl Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing12.0 h
  • Review / QA6.0 h
30.0 hours of engineering $5,120
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $8,192.

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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-2026-5264 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