Vulnerability identifier: #VU18788

Vulnerability risk: Medium

CVSSv3.1: 5.6 [CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:U/RC:C]

CVE-ID: N/A

CWE-ID: CWE-310

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
SymCrypt
Universal components / Libraries / Libraries used by multiple products
Windows
Operating systems & Components / Operating system
Windows Server
Operating systems & Components / Operating system

Vendor: Microsoft

Description

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to an error when calculating the modular inverse on specific bit patterns with bcryptprimitives!SymCryptFdefModInvGeneric() function when processing X.509 certificates. A remote attacker can supply a specially crafted X.509 certificate to the affected system and trigger denial of service conditions.

Any application that uses the vulnerable library, e.g. antivirus software is susceptible to this issue.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

SymCrypt: All versions

Windows: 10 1511 - 10 Gold, 8.1 - 8.1 RT

Windows Server: 2012 - 2019 1903

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External links
http://bugs.chromium.org/p/project-zero/issues/detail?id=1804

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, proof of concept for this vulnerability is available.