Security readout for executives and security teams
Plain-English summary
Adobe Connect 11.2.3 and earlier has a reflected XSS flaw. A victim must be persuaded to open a malicious URL. If successful, attacker-controlled JavaScript may run in that user's browser session, creating limited confidentiality and integrity risk.
Executive priority
Treat as a moderate-priority remediation item. It is not presented as actively exploited, but it can affect user sessions if vulnerable Connect systems remain in use and users open malicious links.
Technical view
CVE-2021-40721 is CWE-79 reflected cross-site scripting in Adobe Connect. CVSS 3.1 is 6.1: network reachable, low complexity, no privileges required, user interaction required, changed scope, low confidentiality and integrity impact, no availability impact.
Likely exposure
Exposure is limited to Adobe Connect deployments running version 11.2.3 or earlier, where users can be induced to open attacker-supplied links referencing vulnerable pages.
Exploitation context
The bundle does not identify CISA KEV inclusion or active exploitation. The documented attack condition requires social engineering: convincing a victim to visit a URL that references a vulnerable Adobe Connect page.
Researcher notes
Evidence is limited to the CVE record and Adobe advisory reference. Do not assume affected builds beyond 11.2.3 and earlier, or specific fixed versions, without consulting APSB21-91 directly.
Mitigation direction
- Inventory Adobe Connect deployments and record exact versions.
- Review Adobe APSB21-91 for vendor-approved updates or workarounds.
- Prioritize remediation for internet-facing or broadly used Connect instances.
- Educate administrators and users to distrust unexpected Connect links.
- Monitor web logs for unusual requests to Connect pages.
Validation and detection
- Confirm whether any Adobe Connect instance is version 11.2.3 or earlier.
- Check change records for remediation aligned to Adobe APSB21-91.
- Verify Connect URLs are not unnecessarily exposed to untrusted networks.
- Review browser-side security reports or logs for suspicious script execution indicators.
- Document whether affected systems are public-facing, internal, or retired.
Public sources used
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
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-79: User-session and phishing behavior lookup
Client-side and session-facing weaknesses should be reviewed alongside initial-access and user-execution behaviors. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-40721 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 6.1 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
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 vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N2.82.7Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
6.1MediumVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://helpx.adobe.com/security/products/connect/apsb21-91.htmlCVE 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.
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.