CVE intelligence and bounded remediation
CVE-2020-36477 — An issue was discovered in Mbed TLS before 2.24.0
An issue was discovered in Mbed TLS before 2.24.0. The verification of X.509 certificates when matching the expected common name (the cn argument of mbedtls_x509_crt_verify) with the actual certificate name is mishandled: when the subjecAltName extension is present, the expected name is compared to any name in that extension regardless of its type. This means that an attacker could impersonate a 4-byte or 16-byte domain by getting a certificate for the corresponding IPv4 or IPv6 address (this would require the attacker to control that IP address, though).
- Severity
- Medium
- CVSS
- 5.9 (3.1)
- Published
- 2021-08-23
- CISA KEV
- Not currently listed
- Ecosystem
- software/application
- Weaknesses
- CWE-295
Affected products
- arm / mbed_tls
Matched remediation archetype
Cryptography, certificate, signature, and channel validation
This catalog composition supplies bounded fallback guidance. Explicitly reviewed curated workflows load with the complete record below.
Check exposure
- Inventory affected algorithms, key uses, trust stores, certificate validation settings, random sources, and plaintext channels across clients and services.
- Determine which secrets, identities, signatures, or data protections depend on the affected primitive or validation path.
- Check debug, compatibility, fallback, and hostname or audience override settings in build and runtime configuration.
Remediate safely
- Use a maintained platform cryptographic API with approved algorithms, modes, parameters, randomness, and full peer identity validation.
- Remove insecure fallback and validation bypasses; separate keys by purpose and load them from managed secret storage.
- Plan rotation or reissuance for affected keys, certificates, tokens, hashes, or ciphertext and document compatibility sequencing.
Authoritative sources
Complete CVE record and remediation plan
The detailed catalog view below loads this exact record, its source evidence, and the full seven-phase agentic change plan.