Vulnerability in github.com/axllent/mailpit (CVE-2026-67445)
Summary
Vulnerability in github.com/axllent/mailpit (CVE-2026-67445). Risk of unauthorized operations or information disclosure. Exploitable via MaxMessageSize. Mitigation: upgrade to 1.30.4 or later.
Original description
The description as published by the source.
Summary
Mailpit's SMTP server reads each command line with an unbounded bufio.Reader.ReadString('\n') before parsing the command or enforcing any protocol length limit. A remote SMTP client can send an oversized single command line and force Mailpit to allocate attacker-controlled memory before the server returns a syntax error or times out, even though RFC 5321 limits SMTP command lines to 512 octets including CRLF.
Technical Details
Mailpit enables SMTP by default. config/config.go sets SMTPListen = "[::]:1025", and cmd/root.go calls smtpd.Listen() during normal startup. The SMTP server configures recipient and message DATA size limits in internal/smtpd/main.go, including the default 50 MiB MaxMessageSize, but those limits do not apply to command lines.
The vulnerable path is in the SMTP command loop. internal/smtpd/smtpd.go calls s.readLine() for every command before parsing the verb or arguments:
line, err := s.readLine()
if err != nil {
if netErr, ok := err.(net.Error); ok && netErr.Timeout() {
s.writef("421 4.4.2 %s %s ESMTP Service closing transmission channel after timeout exceeded", s.srv.Hostname, s.srv.AppName)
}
break
}
verb, args := s.parseLine(line)
readLine() then buffers until newline without a maximum length:
func (s *session) readLine() (string, error) {
if s.srv.Timeout > 0 {
_ = s.conn.SetReadDeadline(time.Now().Add(s.srv.Timeout))
}
line, err := s.br.ReadString('\n'…
Source: NIST National Vulnerability Database 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-2026-67445 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 1.30.4 or later.
If unsure, ask your IT team or search "github.com/axllent/mailpit CVE-2026-67445" on the vendor's site.
CVE-2026-67445 (github.com/axllent/mailpit) — CWE-400 / CVSS v3 5.3
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: MaxMessageSize / srv.MaxSize / NOOP / develop
Patched: 1.30.4 — 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-400) 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 / srv.MaxSize / NOOP / develop.
Severity: Medium (CVSS 5.3/10). Risk of unauthorized operations or information disclosure.
Update to 1.30.4.
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 1.30.4ステージング環境で 1.30.4 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
- web github.com
- web github.com
- web github.com
- web nvd.nist.gov
- web github.com