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CVE Record

CVE-2020-36475: 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). The calculations performed by mbedtls_mpi_exp_mod are not limited; thus, supplying overly large parameters could lead to denial of service when generating Diffie-Hellman key pairs.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

Mbed TLS had an availability weakness in Diffie-Hellman key generation. Systems using vulnerable Mbed TLS versions could spend excessive resources on oversized cryptographic parameters, causing denial of service. The sources identify fixed upstream releases but do not provide CVSS, CWE, or confirmed active exploitation.

Executive priority

Treat this as a moderate availability risk. Prioritize patching where Mbed TLS is used in exposed services, embedded devices, or vendor appliances, but do not treat it as confirmed exploited from the supplied evidence.

Technical view

Before Mbed TLS 2.25.0, 2.16.9 LTS, and 2.7.18 LTS, mbedtls_mpi_exp_mod did not limit calculations. Overly large parameters could exhaust processing during Diffie-Hellman key-pair generation, producing a denial-of-service condition. Exposure depends on whether affected applications accept untrusted parameters into DH generation paths.

Likely exposure

Most likely in embedded, appliance, server, or application stacks bundling Mbed TLS before the named fixed releases, especially where Diffie-Hellman operations can be influenced by external peers or supplied parameters.

Exploitation context

The provided sources do not claim active exploitation, and the CVE is not marked KEV. The described impact is denial of service, not data theft or code execution. Practical risk depends on reachability of the vulnerable DH key-generation path.

Researcher notes

The CVE record lacks CVSS and CWE detail. The core issue is unbounded computation in mbedtls_mpi_exp_mod during Diffie-Hellman key-pair generation. Validate reachability and versioning before escalating severity beyond availability impact.

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 SSA-756638 if Siemens products are in scope.
  • Ask vendors to confirm bundled Mbed TLS versions in appliances and firmware.
  • Prioritize internet-facing or unauthenticated cryptographic endpoints first.

Validation and detection

  • Inventory SBOMs, packages, firmware, and static builds for Mbed TLS versions.
  • Confirm deployed binaries link to fixed Mbed TLS versions.
  • Identify services that perform Diffie-Hellman key generation using peer-controlled inputs.
  • Review Debian package status and vendor advisories for affected products.
  • Record systems where Mbed TLS version cannot be confirmed.
Prepared
Confidence
medium
Sources
8

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
7Source 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.