Security readout for executives and security teams
Plain-English summary
Cisco Firepower Management Center has stored XSS flaws in its web management interface. An authenticated attacker could get an interface user to interact with malicious content, causing script to run in that user’s browser session. Business risk is mainly admin-session abuse and browser-exposed data, not system takeover by itself.
Executive priority
Treat this as a moderate-priority management-plane issue. It is not described as actively exploited, but FMC is security infrastructure; remediation should be scheduled after confirming affected versions and exposure.
Technical view
CVE-2021-1238 is CWE-79 in Cisco FMC’s web interface due to insufficient validation of user input. CVSS is 4.8, with network attack vector, low complexity, high privileges required, user interaction required, changed scope, low confidentiality and integrity impact, and no availability impact.
Likely exposure
Exposure is limited to organizations running Cisco Firepower Management Center. The source bundle does not provide affected version ranges, so teams must confirm installed FMC releases against Cisco’s advisory and local asset records.
Exploitation context
The available sources do not show KEV listing or active exploitation. Exploitation requires an authenticated remote attacker with high privileges and a user interaction condition, limiting broad internet-scale risk but still relevant for management-plane security.
Researcher notes
The record identifies stored XSS in the FMC web interface, but the provided bundle lacks version ranges, fixed releases, and exploit proof status. Avoid assumptions beyond authenticated, remote, user-interaction-based XSS with low confidentiality and integrity impact.
Mitigation direction
- Check Cisco’s advisory for affected releases and fixed software guidance.
- Restrict FMC management access to trusted administrative networks or VPN paths.
- Review and reduce high-privilege FMC accounts where practical.
- Prioritize update planning for externally reachable or broadly accessible management interfaces.
- Monitor vendor guidance for any revised affected-version or remediation information.
Validation and detection
- Inventory all Cisco FMC instances and record installed versions.
- Compare each FMC version against Cisco’s advisory before declaring non-exposure.
- Review who can authenticate to FMC with high privileges.
- Confirm FMC management interfaces are not broadly reachable.
- Look for unusual FMC administrative activity around affected systems.
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-2021-1238 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
- 4.8 (3.0)
- Known Exploited
- No
- Published
Vector: CVSS:3.0/AV:N/AC:L/PR:H/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:3.0/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N1.72.7Primary CVE scoreVulnerability scoring details
Base CVSS 3.0 score
4.8MediumVector: CVSS:3.0/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N
Source materials
- CVE List V5 sourceCVE List V5
- 20210113 Cisco Firepower Management Center Stored Cross-Site Scripting VulnerabilitiesCVE reference · vendor-advisory, x_refsource_CISCO
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.