ZeptoClaw: Email Sender Spoofing to bypass Header-Only From Allowlist Validation
Date: 2026-03
Affected: rust/zeptoclaw
Attack vector: auth-bypass
Category: vulnerability-disclosure
Severity: High
CVE: CVE-2026-32231
CWE: CWE-306
CWE-345
CVSS: 6.5 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N)

### Summary The email channel authorizes senders based on the parsed `From` header identity only. If upstream email authentication/enforcement is weak (for example, relaxed SPF/DKIM/DMARC handling), an attacker can spoof an allowlisted sender address and have the message treated as trusted input. ### Details Relevant code paths: - `src/channels/email_channel.rs:311` extracts sender identity from parsed message headers: - `let from = parsed.from() ... a.address() ...` - `src/channels/email_channel.rs:328` authorizes using that `from` value: - `if !self.is_sender_allowed(&from) { ... }` - `src/channels/email_channel.rs:87` onward (`is_sender_allowed`) performs allowlist/domain matching against the same header-derived value. - There is no in-channel validation of sender authenticity indicators such as SPF/DKIM/DMARC results before allowlist trust decisions. Result: - Trust decision is based on a potentially spoofable header field unless mailbox/provider-side anti-spoofing controls are strong and enforced. ### PoC 1. Configure email channel with strict sender allowlist: - `channels.email.enabled = true` - `channels.email.allowed_senders = ["ceo@example.com"]` - `channels.email.deny_by_default = true` 2. Ensure the monitored mailbox accepts or forwards a spoofed message (for testing, use a local SMTP path that does not enforce sender authentication strongly). 3. Send an email to the monitored inbox with forged header identity: ```bash python - <<'PY' import smtp


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Architectural layers (MAESTRO):