Vulnerability in github.com/axllent/mailpit (CVE-2026-67447)
Summary
Vulnerability in github.com/axllent/mailpit (CVE-2026-67447). Risk of unauthorized operations or information disclosure. Exploitable via MaxMessageSize. Mitigation: upgrade to 1.30.5 or later.
Original description
The description as published by the source.
Summary
Mailpit's SMTP DATA reader enforces the configured MaxMessageSize only after bufio.Reader.ReadBytes('\n') has already buffered a complete DATA line. A remote unauthenticated SMTP client can send one line larger than the configured message-size cap and force memory allocation before Mailpit returns the expected 552 5.3.4 rejection, leaving patched versions still exposed to a single-line incomplete-fix variant of the earlier SMTP DATA body-size issue.
Technical Details
Mailpit enables SMTP by default. The SMTP server now wires config.MaxMessageSize into srv.MaxSize:
if config.MaxMessageSize > 0 {
srv.MaxSize = config.MaxMessageSize * 1024 * 1024
}
The DATA reader then checks that cap, but only after reading a full newline-terminated line into memory:
line, err := s.br.ReadBytes('\n')
if err != nil {
return nil, err
}
if bytes.Equal(line, []byte(".\r\n")) {
break
}
if line[0] == '.' {
line = line[1:]
}
if s.srv.MaxSize > 0 {
if len(data)+len(line) > s.srv.MaxSize {
_, _ = s.br.Discard(s.br.Buffered())
return nil, maxSizeExceeded(s.srv.MaxSize)
}
}
This ordering violates the size-limit invariant. The configured cap can reject the message only after the attacker has supplied the line terminator and ReadBytes('\n') has allocated the over-limit line. With the default 50 MiB cap, a 64 MiB single DATA line is still buffered before Mailpit returns `552 5.3.4 Requested mail action aborted: exc…
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-2026-67447 has been found in github.com/axllent/mailpit.
Attackers can target a specific entry point like MaxMessageSize over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 5.3/10.
What to do: upgrade github.com/axllent/mailpit to 1.30.5 or later.
If unsure, ask your IT team or search "github.com/axllent/mailpit CVE-2026-67447" on the vendor's site.
CVE-2026-67447 (github.com/axllent/mailpit) — CWE-770 / CVSS v3 5.3
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: MaxMessageSize / config.MaxMessageSize / srv.MaxSize / smtp_data_line_size_pov.py
Patched: 1.30.5 — 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.
A vulnerability (CWE-770) exists in github.com/axllent/mailpit. Attackers reach the vulnerable code path via MaxMessageSize without authentication.
Check the vendor advisory for the affected versions of github.com/axllent/mailpit. Attack surface: MaxMessageSize / config.MaxMessageSize / srv.MaxSize / smtp_data_line_size_pov.py.
Severity: Medium (CVSS 5.3/10). Risk of unauthorized operations or information disclosure.
Update to 1.30.5.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. 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。 -
2Apply patch patch
Upgrade github.com/axllent/mailpit to 1.30.5ステージング環境で 1.30.5 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を含めること。
-
3Post-deployment verification verify
Confirm patched version is live in production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。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory nvd.nist.gov
- package github.com
- web github.com
- web github.com
- web github.com
- web github.com