SSRF (Server-Side Request Forgery) in github.com/axllent/mailpit (CVE-2026-55187)
Summary
SSRF in github.com/axllent/mailpit (CVE-2026-55187). Risk of unauthorized operations or information disclosure. Exploitable via POST /api/v1/message/{ID}/link-check. Mitigation: upgrade to 1.30.2 or later.
Original description
The description as published by the source.
Mailpit is an email testing tool and API for developers. Prior to 1.30.2, the remediation shipped for CVE-2026-27808 is incomplete because the tools.IsInternalIP deny-list in internal/tools/net.go relies on Go's standard library classification helpers and does not block IPv6 transition mechanisms or prefixes such as NAT64, 6to4, IPv4-compatible IPv6, ISATAP, fec0::/10, and 2001:db8::/32. An attacker who can deliver email and invoke POST /api/v1/message/{ID}/link-check can coerce the Link Check API's safeDialContext path into dialing internal destinations and can use status-code and error feedback to map internal service reachability, including cloud metadata endpoints. This issue is fixed in version 1.30.2.
Source: GitHub Security Advisories (Global) NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-55187 has been found in github.com/axllent/mailpit.
Attackers can target a specific entry point like POST /api/v1/message/{ID}/link-check over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 5.8/10.
What to do: upgrade github.com/axllent/mailpit to 1.30.2 or later.
If unsure, ask your IT team or search "github.com/axllent/mailpit CVE-2026-55187" on the vendor's site.
CVE-2026-55187 (github.com/axllent/mailpit) — CWE-918 / CVSS v3 5.8
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: POST /api/v1/message/{ID}/link-check / tools.IsInternalIP / IsLoopback / IsPrivate
Patched: 1.30.2 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
SSRF (CWE-918) exists in github.com/axllent/mailpit. Attackers reach the vulnerable code path via POST /api/v1/message/{ID}/link-check without authentication.
Check the vendor advisory for the affected versions of github.com/axllent/mailpit. Attack surface: POST /api/v1/message/{ID}/link-check / tools.IsInternalIP / IsLoopback / IsPrivate.
Severity: Medium (CVSS 5.8/10). Risk of unauthorized operations or information disclosure.
Update to 1.30.2.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual POST /api/v1/message/{ID}/link-check requests with malformed payloads or SQL meta-characters. Run grep -r 'github.com/axllent/mailpit' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'github.com/axllent/mailpit' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
github.com/axllent/mailpitを grep し、稼働しているサービス・バージョンを把握する。 -
2Hunt for indicators of compromise detect
grep 'POST /api/v1/message/{ID}/link-check' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'アクセスログで
POST /api/v1/message/{ID}/link-checkへの異常なリクエスト (不正な認証ヘッダ・SQLメタ文字)を過去 30〜90日分捜索。WAF/SIEM があれば該当パスのアラート発火履歴を確認。 -
3Apply patch patch
Upgrade github.com/axllent/mailpit to 1.30.2ステージング環境で 1.30.2 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスと、Step 2 で見つけた異常検知の続報チェックを含めること。
-
4Post-deployment verification verify
Replay attack against POST /api/v1/message/{ID}/link-check on staging to confirm patch closes the vectorパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番では Step 2 と同じログクエリでアラート再発が無いか継続監視。
Affected packages
References
- advisory github.com
- advisory nvd.nist.gov
- advisory github.com
- package github.com
- patch github.com
- web github.com
- web github.com