Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:NSummary
CVE-2026-27808 is a medium-severity SSRF (CWE-918) vulnerability in Axllent Mailpit. Its CVSS base score is 5.8 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 38th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified map to AC-4 (Information Flow Enforcement) and SI-10 (Information Input Validation) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
Mailpit, an email testing tool and API for developers, is affected by CVE-2026-27808, a Server-Side Request Forgery (SSRF) vulnerability in the Link Check API endpoint (/api/v1/message/{ID}/link-check) prior to version 1.29.2. The server performs HTTP HEAD requests to every URL found in an email without validating target hosts or filtering private/internal IP addresses. This results in a non-blind SSRF, as the response includes status codes and status text per link, classified under CWE-918 with a CVSS v3.1 score of 5.8 (AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N).
Remote attackers can exploit this vulnerability in the default configuration, which lacks authentication on SMTP or API endpoints, requiring zero user interaction. By sending an email containing arbitrary URLs to Mailpit and triggering the Link Check API, attackers force the server to issue requests to attacker-controlled hosts, including private or internal IP addresses. Attackers receive feedback on these requests via the returned status information, enabling reconnaissance or access to internal resources with low confidentiality impact.
Version 1.29.2 addresses this vulnerability. Security advisories recommend updating to this version or later for mitigation. Details are provided in the GitHub security advisory GHSA-mpf7-p9x7-96r3, release notes at https://github.com/axllent/mailpit/releases/tag/v1.29.2, and the fixing commit at https://github.com/axllent/mailpit/commit/10ad4df8cc0cd9e51dea1b4410009545eef7fbf5.
This SSRF vulnerability shares the same class as prior issues fixed in Mailpit's HTML Check API (CVE-2026-23845 / GHSA-6jxm-fv7w-rw5j) and screenshot proxy (CVE-2026-21859 / GHSA-8v65-47jx-7mfr), but the Link Check code path was not included in those patches. The CVE was published on 2026-02-26.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-8775
Vulnerability Data
Mailpit is an email testing tool and API for developers. Prior to version 1.29.2, the Link Check API (/api/v1/message/{ID}/link-check) is vulnerable to Server-Side Request Forgery (SSRF). The server performs HTTP HEAD requests to every URL found in an email without…
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validating target hosts or filtering private/internal IP addresses. The response returns status codes and status text per link, making this a non-blind SSRF. In the default configuration (no authentication on SMTP or API), this is fully exploitable remotely with zero user interaction. This is the same class of vulnerability that was fixed in the HTML Check API (CVE-2026-23845 / GHSA-6jxm-fv7w-rw5j) and the screenshot proxy (CVE-2026-21859 / GHSA-8v65-47jx-7mfr), but the Link Check code path was not included in either fix. Version 1.29.2 fixes this vulnerability.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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V1.3.6V1.5.3V5.3.2V10.4.7
Mitigating Controls (NIST 800-53 r5) AI
Information flow enforcement can restrict which destinations the server is allowed to contact on behalf of users.
Input validation directly stops untrusted URLs from being accepted and fetched without destination checks.
Boundary protection limits the network reach of server-initiated requests even if SSRF occurs.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure development practices directly include input validation and destination allow-listing that prevent SSRF.
Runtime monitoring of web applications and services can detect anomalous outbound requests indicative of SSRF.
Vulnerability identification processes can discover and record SSRF flaws in web applications.
Network segmentation and egress controls can limit the damage from successful SSRF requests.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Operational threat data describing SSRF campaigns can be used to tighten outbound-request allow-lists and detection rules before attackers exploit them.