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CVE Record

CVE-2020-36478: An issue was discovered in Mbed TLS before 2.25.0 (and before 2.16.9 LTS and before 2.7.18 LTS).

An issue was discovered in Mbed TLS before 2.25.0 (and before 2.16.9 LTS and before 2.7.18 LTS). A NULL algorithm parameters entry looks identical to an array of REAL (size zero) and thus the certificate is considered valid. However, if the parameters do not match in any way, then the certificate should be considered invalid.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2020-36478 is a certificate validation flaw in Mbed TLS. A malformed certificate parameter combination could be treated as valid when it should be rejected. This matters where Mbed TLS protects device, application, or service trust decisions. Sources do not provide CVSS, CWE, or evidence of active exploitation.

Executive priority

Treat as a targeted trust-chain remediation item, not an emergency based on current evidence. Prioritize internet-facing, embedded, and authentication-sensitive systems using Mbed TLS, especially where vendor firmware updates may lag.

Technical view

Mbed TLS before 2.25.0, 2.16.9 LTS, and 2.7.18 LTS could confuse NULL algorithm parameters with a zero-length REAL array during certificate validation. If parameters did not match, the certificate should have been invalid, but could be accepted. Public detail is limited.

Likely exposure

Exposure is most likely in products, firmware, applications, and Linux packages that embed or link vulnerable Mbed TLS releases. Debian and Siemens references indicate downstream impact, but the bundle does not identify specific affected Siemens products or all dependent software.

Exploitation context

The source bundle does not show CISA KEV listing or active exploitation. The issue appears relevant to certificate trust validation, so practical risk depends on whether a deployment relies on affected Mbed TLS certificate parsing in reachable authentication or TLS paths.

Researcher notes

Evidence supports a version-bounded Mbed TLS validation flaw, but public details in the bundle are sparse. Do not assume broad exploitability without confirming reachable certificate-validation usage and affected library versions. No exploit status is evidenced beyond vendor and distro updates.

Mitigation direction

  • Upgrade Mbed TLS to 2.25.0, 2.16.9 LTS, 2.7.18 LTS, or later supported releases.
  • Apply Debian LTS mbedtls security updates where Debian packages are used.
  • Check Siemens and other product-vendor advisories for firmware or appliance-specific fixes.
  • Identify statically linked Mbed TLS copies and rebuild affected applications.
  • Prioritize systems using Mbed TLS for TLS, certificate authentication, or device trust decisions.

Validation and detection

  • Inventory Mbed TLS versions in packages, containers, firmware, and embedded application builds.
  • Confirm whether applications use Mbed TLS certificate validation code paths.
  • Review SBOMs and build manifests for bundled or statically linked Mbed TLS.
  • Verify patched runtime versions after package or firmware updates.
  • Track vendor advisories for products that do not expose library versions directly.
Prepared
Confidence
medium
Sources
9

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
8Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.