What’s Vulnerable › Vulnerabilities

CVE-2021-34823

• Severity: critical (CVSS 9.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 2.0% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-08-13 · updated 2026-06-17
• Weakness: CWE-611

Description

The ON24 ScreenShare (aka DesktopScreenShare.app) plugin before 2.0 for macOS allows remote file access via its built-in HTTP server. This allows unauthenticated remote users to retrieve files accessible to the logged-on macOS user. When a remote user sends a crafted HTTP request to the server, it triggers a code path that will download a configuration file from a specified remote machine over HTTP. There is an XXE flaw in processing of this configuration file that allows reading local (to macOS) files and uploading them to remote machines.

Affected products

• ON24 Screenshare: before 2.0 — fixed in 2.0

How to fix

Upgrade to a fixed version: ON24 Screenshare 2.0. Check the vendor advisory for mitigations.

References

• https://www.trustwave.com/en-us/resources/security-resources/security-advisories/
• https://www.trustwave.com/en-us/resources/security-resources/security-advisories/?fid=29105
• https://www.trustwave.com/en-us/resources/security-resources/security-advisories/
• https://www.trustwave.com/en-us/resources/security-resources/security-advisories/?fid=29105

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