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WolfsslApplication

CVE-2026-4395

CRITICAL · 9.8 CVSS v3.1 Published 2026-03-19
Fix available
A fix is available. Upgrade to 5.9.0 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-based buffer overflow in the KCAPI ECC code path of wc_ecc_import_x963_ex() in wolfSSL wolfcrypt allows a remote attacker to write attacker-controlled data past the bounds of the pubkey_raw buffer via a crafted oversized EC public key point. The WOLFSSL_KCAPI_ECC code path copies the input to key->pubkey_raw (132 bytes) using XMEMCPY without a bounds check, unlike the ATECC code path which includes a length validation. This can be triggered during TLS key exchange when a malicious peer sends a crafted ECPoint in ServerKeyExchange.

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

Heap-based buffer overflow in wolfSSL's KCAPI ECC code path where wc_ecc_import_x963_ex() copies an attacker-controlled EC public key point to a fixed 132-byte buffer (key->pubkey_raw) using XMEMCPY without bounds validation. During TLS key exchange, a malicious peer can send a crafted oversized ECPoint in ServerKeyExchange to write data past the buffer bounds.

MitigationUpdate wolfSSL to the patched version that adds proper length validation before the XMEMCPY operation in the KCAPI code path, similar to the protection already present in the ATECC code path.

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:< 5.9.0

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
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. Identify wolfSSL version
    Run 'wolfssl version' or check the library linked in your application. On Linux: ldd <executable> | grep wolfssl, or check the header file wolfssl/version.h for WOLFSSL_VERSION. On embedded systems, check the build configuration or firmware metadata.
    Affected if The installed version is below 5.9.0
  2. Confirm KCAPI module is enabled
    Check the wolfSSL build configuration. Look for --enable-kcapi or HAVE_KCAPI in build flags. On systems using autotools: 'grep -i kcapi config.log' or 'grep -i kcapi .libs/built-with'. On embedded builds, check the generated user_settings.h for '#define HAVE_KCAPI' or '#define WOLFSSL_KCAPI'.
    Affected if KCAPI support (HAVE_KCAPI or WOLFSSL_KCAPI) is defined in the build configuration
  3. Verify ECC is enabled
    Check the build configuration for ECC support. Look for '--enable-ecc' or '#define HAVE_ECC' in the build configuration files. On Linux: 'grep -i ecc .libs/built-with' or check user_settings.h.
    Affected if ECC (HAVE_ECC) is enabled in the build
  4. Confirm TLS is active
    Determine if the application uses wolfSSL for TLS operations. Check if the process links to wolfSSL and accepts or makes TLS connections. For servers: verify they accept TLS connections (check listening services or application logs).
    Affected if The application uses wolfSSL for TLS server or client connections, particularly those performing EC key exchanges

You are affected if your wolfSSL version is below 5.9.0 AND your build has KCAPI enabled (HAVE_KCAPI defined) AND ECC is compiled in, and the system performs TLS connections using EC key exchange.

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 5.9.0 or later
Fixed in 5.9.0
Vendor patch github.com →
Interim mitigation

Update wolfSSL to the patched version that adds proper length validation before the XMEMCPY operation in the KCAPI code path, similar to the protection already present in the ATECC code path.

Recommended fix High confidence

wolfSSL 5.9.0 or later

  1. 1. Identify all systems and applications that use wolfSSL library version < 5.9.0
  2. 2. In a non-production environment, upgrade wolfSSL to version 5.9.0 or later from https://www.wolfssl.com/download/ or your distribution's package manager
  3. 3. Rebuild and recompile any applications statically linked against the old wolfSSL library
  4. 4. Verify the upgrade by confirming the new version (e.g., run wolfSSL version check or inspect library binary)
  5. 5. Test TLS/EC key exchange functionality to ensure normal operation
  6. 6. Deploy the upgraded wolfSSL to production systems

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

Fix this in Wolfssl Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing4.0 h
  • Review / QA2.0 h
10.0 hours of engineering $1,720
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,752.

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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-2026-4395 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