CVE-2023-35373Network attack vector

Authenticode trust spoofing via missing EKU validation

Published Jul 11, 2023 · Updated Jan 1, 2025

Improper signature verification in Microsoft Mono 6.12.0 before 6.12.0.200 allows remote authenticated users to spoof Authenticode trust. AuthenticodeDeformatter accepts a signer certificate without requiring its Extended Key Usage extension to contain the code-signing OID. Exposure is limited to applications that invoke AuthenticodeDeformatter or the chktrust tool, and successful abuse makes an unqualified signer appear trusted.

CVSS severity5.3
Medium
EPSS probability0.80%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Improper signature verification in Microsoft Mono 6.12.0 before 6.12.0.200 allows remote authenticated users to spoof Authenticode trust. AuthenticodeDeformatter accepts a signer certificate without requiring its Extended Key Usage extension to contain the code-signing OID. Exposure is limited to applications that invoke AuthenticodeDeformatter or the chktrust tool, and successful abuse makes an unqualified signer appear trusted.

The record

CVE
CVE-2023-35373
Published
Jul 11, 2023
Updated
Jan 1, 2025
Vendor
Microsoft
Product
Mono
Classifications
CWE-347, T1553.002
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 11, 2023CVE publishedPublication date reported by the CVE source.
  2. Jan 1, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=6.12.0 <6.12.0.200

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Microsoft · Monoversion=6.12.0 <6.12.0.200

Published CVSS scores

5.3NIST NVDCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N
5.3Microsoft CorporationCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-347Improper Verification of Cryptographic Signature
T1553.002Subvert Trust Controls: Code Signing

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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo