Passbolt API before 5, if the server is misconfigured (with an incorrect installation process and disregarding of Health Check results), can send email messages with a domain name taken from an attacker-controlled HTTP Host header.
Conclusion & alert: CVE-2025-27913 is rated Low Risk (18.9/100): CVSS Low severity, with low exploitation likelihood (EPSS 0.11%). Mandatory action: Low composite risk—no urgent action required; patch on your normal maintenance cycle and revisit priority if CVSS or EPSS increases.
Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.
EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).
| # | Date | Old EPSS score | New EPSS score | Delta (New - Old) |
|---|---|---|---|---|
| 1 | 2026-04-23 | 0.15% | 0.11% | -0.04% |
| 2 | 2026-04-19 | 0.05% | 0.15% | +0.10% |
| 3 | 2025-11-24 | — | 0.05% | — |
Full EPSS history (6 records total)
CVSS metrics for this CVE.
| Base score | Version | Severity | Vector | Exploitability | Impact | Score source |
|---|---|---|---|---|---|---|
| 2.1 | 4.0 | LOW |
|
— | — | [email protected] |
| 7.5 | 3.1 | HIGH |
|
3.9 | 3.6 | 134c704f-9b21-4f2e-91b3-4a467353bcc0 |
| Vendor | Product | Version | Raw CPE |
|---|---|---|---|
| passbolt | passbolt_api | < 5.0.0 | cpe:2.3:a:passbolt:passbolt_api:*:*:*:*:*:*:*:* |
| URL | Tags |
|---|---|
| https://www.passbolt.com/incidents/host-header-injection | Mitigation Vendor Advisory |