SSRF in Axllent Mailpit
CVE-2026-21859
Mailpit is an email testing tool and API for developers. Versions 1.28.0 and below have a Server-Side Request Forgery (SSRF) vulnerability in the /proxy endpoint, allowing attackers to make requests to internal network resources. The /proxy endpoint validates http:// and https:// schemes, but it does not block internal IP addresses, enabling attackers to access internal services and APIs. This vulnerability is limited to HTTP GET requests with minimal headers. The issue is fixed in version 1.28.1.
Vulnerability class: SSRF (Server-Side Request Forgery)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.8 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N.
EPSS exploit prediction
EPSS: 0.008 (56.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 57th percentile — 56.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.008 · newest: 0.008 · change: -0.000
Affected products
- Axllent Mailpit — versions < 1.28.1
Weakness classification (CWE)
References
- github.com/axllent/mailpit/security/advisories/GHSA-8v65-47jx-7mfr (Exploit, Vendor Advisory)
- github.com/axllent/mailpit/commit/3b9b470c093b3d20b7d751722c1c24f3eed2e19d (Patch)
Frequently asked questions
- What is CVE-2026-21859?
- CVE-2026-21859 is a medium-severity vulnerability in Axllent Mailpit, classified under Server-Side Request Forgery (SSRF). CVSS score: 5.8/10. Published 2026-01-08.
- How severe is CVE-2026-21859?
- Medium severity. CVSS v3 base score is 5.8 out of 10.