CVE-2021-41991: The in-memory certificate cache in strongSwan before 5.9.4 has a remote integer overflow upon receiving many requests with different certificates to fill the cache and later trigger the replacement of cache entries. The code attempts to select a less-often-used cache entry by means of a random number generator but this is not done correctly. Remote code execution might be a slight possibility.

Overview

Severity

High (CVSS 7.5)

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Exploit Status

Not Exploited

Patch Tuesday

2021-Oct

Released

2021-10-22

Last Updated

2021-12-16

EPSS Score

2.54% (percentile: 85.4%)

FAQ

Is Azure Linux the only Microsoft product that includes this open-source library and is therefore potentially affected by this vulnerability? One of the main benefits to our customers who choose to use the Azure Linux distro is the commitment to keep it up to date with the most recent and most secure versions of the open source libraries with which the distro is composed. Microsoft is committed to transparency in this work which is why we began publishing CSAF/VEX in October 2025. See this blog post for more information. If impact to additional products is identified, we will update the CVE to reflect this.

Affected Products (2)

Other

• 18977-16820
• 18902-16823

Revision History

• 2021-10-22: Information published.
• 2021-12-16: Added strongswan to CBL-Mariner 2.0