{"schema_version":"1.7.3","id":"GHSA-8v65-47jx-7mfr","published":"2026-01-06T17:44:29Z","modified":"2026-02-03T03:13:30.492241Z","aliases":["CVE-2026-21859","GO-2026-4284"],"summary":"Mailpit Proxy Endpoint has Server-Side Request Forgery (SSRF) vulnerability","details":"## Summary\n\nA Server-Side Request Forgery (SSRF) vulnerability exists in Mailpit's `/proxy` endpoint that allows attackers to make requests to internal network resources.\n\n\n## Description\n\nThe `/proxy` endpoint allows requests to internal network resources. While it validates `http://` and `https://` schemes, it does not block internal IP addresses, allowing attackers to access internal services and APIs.\n\n## Proof of Concept\n\n### Basic SSRF Request\n```\nGET /proxy?url=http://127.0.0.1:8025/api/v1/info\n```\n\nThis returns internal API data including database path and runtime statistics.\n \n## Impact Assessment\n\n### 1. Internal Network Scanning\nAttacker can probe and discover internal services on the network.\n\n### 2. Information Disclosure\nAccess to internal API data, database paths, and runtime statistics.\n\n### 3. Email Content Access\nAbility to read all captured emails via internal API endpoints.\n\n### 4. Cloud Metadata Access\nIf deployed in cloud environments (AWS/GCP/Azure), potential access to instance metadata services (e.g., `http://169.254.169.254/`).\n\n## Attack Scenarios\n\n### Scenario 1: Development Environment Exposure\nIf Mailpit is accidentally exposed to the internet, attackers can leverage SSRF to access internal development resources and services.\n\n### Scenario 2: Container Escape Information\nIn containerized deployments, SSRF can reveal container metadata and internal service configurations.\n\n### Scenario 3: Lateral Movement\nIn corporate networks, SSRF can be used to discover and interact with internal services, facilitating lateral movement.\n\n## Mitigating Factors\nThis vulnerability is limited to HTTP GET requests with minimal headers. Additionally, Mailpit's web UI & API should be protected by basic authentication when exposed to the internet, which prevents access to the proxy endpoint. \n\n## References\n\n- [MDN Web Security - SSRF Attacks](https://developer.mozilla.org/en-US/docs/Web/Security/Attacks/SSRF)\n- [CWE-918: Server-Side Request Forgery](https://cwe.mitre.org/data/definitions/918.html)\n- [OWASP SSRF Prevention Cheat Sheet](https://cheatsheetseries.owasp.org/cheatsheets/Server_Side_Request_Forgery_Prevention_Cheat_Sheet.html)","affected":[{"package":{"name":"github.com/axllent/mailpit","ecosystem":"Go","purl":"pkg:golang/github.com/axllent/mailpit"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"1.28.1"}]}],"database_specific":{"last_known_affected_version_range":"<= 1.28.0","source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/01/GHSA-8v65-47jx-7mfr/GHSA-8v65-47jx-7mfr.json"}}],"references":[{"type":"WEB","url":"https://github.com/axllent/mailpit/security/advisories/GHSA-8v65-47jx-7mfr"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-21859"},{"type":"WEB","url":"https://github.com/axllent/mailpit/commit/3b9b470c093b3d20b7d751722c1c24f3eed2e19d"},{"type":"PACKAGE","url":"https://github.com/axllent/mailpit"},{"type":"WEB","url":"https://pkg.go.dev/vuln/GO-2026-4284"}],"database_specific":{"cwe_ids":["CWE-918"],"github_reviewed":true,"github_reviewed_at":"2026-01-06T17:44:29Z","nvd_published_at":"2026-01-08T00:16:00Z","severity":"MODERATE"},"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N"}]}