Security readout for executives and security teams
Plain-English summary
Mautic can permanently store attacker-supplied script content through an unauthenticated bounce-management callback. The script runs later when a logged-in Mautic user opens an affected contact or lead detail page. That creates business risk around CRM data tampering, session compromise, and unauthorized access to marketing/contact information.
Executive priority
Treat this as a high-priority remediation for exposed Mautic systems, especially production marketing or CRM environments. The risk depends on webhook exposure and user access patterns, but unauthenticated stored XSS can create meaningful data integrity and confidentiality impact.
Technical view
CVE-2021-27910 is stored XSS in Mautic’s bounce callback handling. The unauthenticated POST callback path stores insufficiently sanitized values from error and error_related_to, then executes them in the lead details view. CVSS 3.1 is 8.2 with network access, low complexity, no privileges, and required user interaction.
Likely exposure
Exposure is most likely where Mautic bounce management webhooks are enabled and reachable from the internet. The source identifies Mailjet webhook handling and assumes similar behavior across webhook types. Affected versions are not specified in the provided bundle.
Exploitation context
The provided sources do not show CISA KEV listing or confirmed active exploitation. The issue is still important because the callback requires no authentication and the stored payload triggers when an authenticated user views the affected lead.
Researcher notes
Evidence supports stored XSS through error and error_related_to in the bounce callback, with execution in authenticated lead detail views. The bundle does not specify affected version ranges, fixed versions, exploit observations, or complete vendor mitigation details.
Mitigation direction
- Review the Mautic advisory and apply the vendor-supported fixed release if applicable.
- Restrict bounce callback reachability to expected webhook sources where operationally feasible.
- Review stored bounce error fields and remove confirmed malicious script content.
- Monitor Mautic admin activity for unusual lead access or data changes.
- Do not rely on unverified workarounds instead of vendor guidance.
Validation and detection
- Inventory Mautic instances and identify internet-facing bounce callback endpoints.
- Check deployed Mautic versions against the GitHub security advisory.
- Confirm whether bounce management webhooks are enabled, especially Mailjet callbacks.
- Review lead detail fields populated from bounce errors for unsafe stored content.
- Verify authenticated lead detail pages render stored bounce data safely.
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 lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-27910 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
- High
- CVSS
- 8.2 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/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:H/A:N2.84.7Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
8.2HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/mautic/mautic/security/advisories/GHSA-86pv-95mj-7w5fCVE 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.