Security readout for executives and security teams
Plain-English summary
CVE-2021-34823 affects the ON24 ScreenShare macOS plugin before version 2.0. If the plugin's built-in HTTP server is reachable, an unauthenticated remote user may be able to make the logged-in user's Mac read and send local files to another system.
Executive priority
Treat this as a high-priority endpoint data exposure risk if ON24 ScreenShare was deployed. The issue can expose user-accessible local files without authentication when reachable.
Technical view
The vulnerable DesktopScreenShare.app component exposes a built-in HTTP server. A crafted HTTP request can trigger retrieval of a remote configuration file; XXE processing of that file can read local macOS files accessible to the logged-on user and upload them remotely.
Likely exposure
Exposure is limited to macOS systems with ON24 ScreenShare/DesktopScreenShare.app versions before 2.0, especially where the plugin is installed, running, and reachable over the network.
Exploitation context
The source bundle does not show CISA KEV listing or active exploitation evidence. The described attack is unauthenticated remote file access through crafted HTTP interaction with the plugin's local server.
Researcher notes
Evidence is concise but specific: vulnerable versions are before 2.0, impact is local file read and remote upload, and the mechanism involves XXE during configuration processing. No CVSS, CWE, patch advisory text, or exploitation-in-the-wild evidence is included.
Mitigation direction
- Inventory macOS endpoints for ON24 ScreenShare/DesktopScreenShare.app installations.
- Remove the plugin where it is no longer required.
- Upgrade versions before 2.0 to 2.0 or later where available.
- Restrict network reachability to the plugin's built-in HTTP server.
- Check ON24 or Trustwave guidance for current remediation details.
Validation and detection
- Confirm installed DesktopScreenShare.app versions across managed macOS endpoints.
- Identify endpoints where the plugin process or HTTP listener is active.
- Review network telemetry for unexpected plugin-related HTTP downloads or uploads.
- Assess whether sensitive files were accessible to logged-on affected users.
- Document systems that cannot be upgraded or removed.
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
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CVE-2021-34823 mapping review
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Open ATT&CK lookup- Severity
- Unknown
- CVSS
- Not scored
- Known Exploited
- No
- Published
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS and timeline data
No CVSS vectors or timeline events were available in the normalized CVE source material.
Source materials
- CVE List V5 sourceCVE List V5
- https://www.trustwave.com/en-us/resources/security-resources/security-advisories/CVE reference · x_refsource_MISC
- https://www.trustwave.com/en-us/resources/security-resources/security-advisories/?fid=29105CVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.