Security readout for executives and security teams
Plain-English summary
This issue means the Kemp LoadMaster WAF in version 7.2.54.1 may miss some XSS content involving onmouseover. A WAF bypass does not necessarily compromise the LoadMaster itself, but it can weaken protection for applications behind it.
Executive priority
Treat this as a moderate-priority defense-in-depth issue. It should be scheduled for normal patch and exposure review, with higher urgency if public applications depend heavily on this WAF for XSS protection.
Technical view
CVE-2021-41823 is a CWE-79 cross-site scripting protection bypass in the Web Application Firewall of Kemp LoadMaster 7.2.54.1. CVSS 3.1 is 6.1, network exploitable, low complexity, no privileges required, and requires user interaction.
Likely exposure
Exposure is most likely where Kemp LoadMaster 7.2.54.1 WAF is deployed to filter XSS for public web applications. The source bundle does not provide CPEs or a broader affected-version range.
Exploitation context
The bundle does not indicate CISA KEV listing or active exploitation. Public references exist, but the provided evidence only supports a protection-bypass condition, not confirmed exploitation in the wild.
Researcher notes
The record is sparse: affected CPEs are not provided, and the only named version is LoadMaster 7.2.54.1. Analysis should avoid extrapolating affected versions until vendor documentation confirms scope.
Mitigation direction
- Check Kemp or Progress guidance for fixed versions or WAF rule updates.
- Upgrade or patch LoadMaster if vendor guidance identifies a corrected release.
- Do not rely on WAF filtering as the only XSS control.
- Harden protected applications with output encoding and context-aware input handling.
- Review WAF policies and monitoring for XSS-related traffic.
Validation and detection
- Inventory LoadMaster appliances and confirm deployed firmware versions.
- Identify applications relying on LoadMaster WAF XSS protection.
- Check whether version 7.2.54.1 is present in production or internet-facing paths.
- Run authorized, controlled XSS-filter validation with safe internal test cases.
- Verify application-side XSS defenses on protected routes.
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-2021-41823 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://pastebin.com/kpx9NvbfCVE reference
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.