CVE-2020-36475Network attack vector

Service interruption via unbounded modular exponentiation

Published Aug 23, 2021 · Updated Aug 4, 2024

Resource exhaustion in Mbed TLS before 2.25.0 allows remote attackers to interrupt services during Diffie-Hellman key generation. The mbedtls_mpi_exp_mod routine accepts attacker-controlled multiprecision parameters without limiting their size, so modular exponentiation can consume excessive processor time. An unauthenticated network peer must reach an application path that generates finite-field Diffie-Hellman key pairs; successful input can stall that service without reading or modifying data.

CVSS severity7.5
High
EPSS probability1.97%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in Mbed TLS before 2.25.0 allows remote attackers to interrupt services during Diffie-Hellman key generation. The mbedtls_mpi_exp_mod routine accepts attacker-controlled multiprecision parameters without limiting their size, so modular exponentiation can consume excessive processor time. An unauthenticated network peer must reach an application path that generates finite-field Diffie-Hellman key pairs; successful input can stall that service without reading or modifying data.

The record

CVE
CVE-2020-36475
Published
Aug 23, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-131, T1499.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 23, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.0NIST National Vulnerability DatabaseAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-131Incorrect Calculation of Buffer Size
T1499.002Service Exhaustion Flood

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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