EUVD-2026-39544
GHSA-68g3-7fhp-7rg3
Severity by source
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Network vector applies as chain is supplied over TLS, but AC:H reflects the prerequisite MITM/chain-control position and non-default build configuration; integrity-only, limited impact, no scope change.
Primary rating from Vendor (wolfSSL).
CVSS VectorVendor: wolfSSL
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Lifecycle Timeline
3DescriptionCVE.org
Chain intermediate CA:TRUE without keyCertSign accepted as a signing CA. Intermediate CA certificates are required to have the keyCertSign key usage when a Key Usage extension is present, but chain-supplied temporary CAs (WOLFSSL_TEMP_CA) added while building a certificate path were previously exempted from this check, so an intermediate asserting CA:TRUE but lacking keyCertSign was accepted as a signing CA. The check now applies to chain-supplied temporary CAs as well; only operator-loaded root certificates (WOLFSSL_USER_CA) and self-signed roots remain exempt. Per RFC 5280 an absent Key Usage extension implies all usages, so the requirement is enforced only when the extension is actually present (extKeyUsageSet). Affects the OpenSSL-compatibility certificate-path-building path (X509_verify_cert / X509_STORE, OPENSSL_EXTRA/OPENSSL_ALL), where untrusted chain intermediates are added as temporary CAs; native (non-OpenSSL-compat) certificate verification does not create temporary CAs and is unaffected. Within those builds, the check applies unless ALLOW_INVALID_CERTSIGN is defined.
AnalysisAI
Certificate chain validation bypass in wolfSSL's OpenSSL-compatibility layer permits a crafted intermediate CA certificate asserting CA:TRUE but missing the keyCertSign key usage bit to be accepted as a valid signing CA during path building. Affected deployments are those compiled with OPENSSL_EXTRA or OPENSSL_ALL that use the X509_verify_cert/X509_STORE API; native wolfSSL verification is entirely unaffected. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires all of the following to be simultaneously true: (1) the target application uses wolfSSL compiled with OPENSSL_EXTRA or OPENSSL_ALL; (2) the application uses X509_verify_cert or X509_STORE for certificate path building (the OpenSSL-compat path); (3) the build does NOT define ALLOW_INVALID_CERTSIGN; and (4) the attacker can supply a crafted untrusted chain intermediate - either via a MITM position on a TLS connection where the peer provides its own chain, or by controlling a subordinate CA that issues certificates consumed by the verifier. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 4.0 score of 6.3 with vector AV:N/AC:L/AT:P/PR:N/UI:N reflects a medium-severity flaw. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker with a MITM position on a TLS connection to an application using wolfSSL's OpenSSL-compat verification path presents a crafted certificate chain containing an intermediate certificate that asserts CA:TRUE in the Basic Constraints extension but includes a Key Usage extension that does not set the keyCertSign bit. The vulnerable AddCA() logic accepts this intermediate as WOLFSSL_TEMP_CA without checking the keyCertSign requirement, allowing the attacker to then present an end-entity certificate signed by this malformed intermediate that passes chain validation. … |
| Remediation | The upstream fix is available as GitHub PR #10702 (https://github.com/wolfSSL/wolfssl/pull/10702); a tagged release version containing this fix is not independently confirmed from available data - consult the wolfSSL security advisory at https://www.wolfssl.com/docs/security-vulnerabilities/ for the confirmed patched release and upgrade to that version. … Detailed patch versions, workarounds, and compensating controls in full report. |
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Same weakness CWE-295 – Improper Certificate Validation
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External POC / Exploit Code
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