CVE-2020-9433Network attack vector

Endpoint impersonation via negative certificate-check results

Published Feb 27, 2020 · Updated Aug 4, 2024

Improper certificate validation in lua-openssl 0.7.7-1 allows man-in-the-middle attackers to impersonate endpoints using malformed certificates. openssl_x509_check_email passes every nonzero X509_check_email result to lua_pushboolean, causing internal-error and malformed-input results to become true. Exploitation requires a client application to use check_email for peer identity validation and accept an attacker-supplied invalid certificate.

CVSS severity9.1
Critical
EPSS probability0.84%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper certificate validation in lua-openssl 0.7.7-1 allows man-in-the-middle attackers to impersonate endpoints using malformed certificates. openssl_x509_check_email passes every nonzero X509_check_email result to lua_pushboolean, causing internal-error and malformed-input results to become true. Exploitation requires a client application to use check_email for peer identity validation and accept an attacker-supplied invalid certificate.

The record

CVE
CVE-2020-9433
Published
Feb 27, 2020
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-295, T1557
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 27, 2020CVE 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

6.4NIST NVDAV:N/AC:L/Au:N/C:P/I:P/A:N
9.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-295Improper Certificate Validation
T1557Adversary-in-the-Middle

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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