GHSA-v3q9-hj7j-63hq
GHSA-v3q9-hj7j-63hq is a CWE-77 vulnerability in aiosmtplib. O3 Security confirms whether GHSA-v3q9-hj7j-63hq is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
aiosmtplib vulnerable to SMTP command injection via CR/LF in sender/recipient address
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-v3q9-hj7j-63hq.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Real-World Exposure
aiosmtplibReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Summary
aiosmtplib's SMTP.mail(), SMTP.rcpt(), SMTP.vrfy() and SMTP.expn() send the caller-supplied email address to the server without rejecting embedded CR/LF (\r\n) bytes. An address that contains a CR/LF is written verbatim onto the SMTP control connection, so the bytes after the CRLF are framed by the server as one or more additional, standalone SMTP command lines. A caller that passes an attacker-influenced sender or recipient address into mail()/rcpt() (or vrfy()/expn()) therefore allows SMTP command injection (CWE-93 / CWE-77): the attacker can smuggle arbitrary SMTP verbs such as MAIL FROM, RCPT TO, RSET, DATA, or AUTH into the session. Injected commands will cause the SMTP instance to hang, but all commands required to complete the envelope could be sent in one address string.
The SMTP.sendmail() command will pass sender and recipient addresses verbatim through to SMTP.mail() & SMTP.rcpt(), and so is also vulnerable. SMTP.send_message() is not affected.
Impact
Severity: medium. Type: SMTP protocol command injection (CWE-93 — Improper Neutralization of CRLF Sequences; CWE-77 — Command Injection).
When an application built on aiosmtplib derives the envelope sender or any recipient from data an attacker can influence (a web form etc.) and passes it to mail()/rcpt() (directly, or via sendmail()/send() without a Message object), the attacker can:
- desynchronize the command/response pipeline and cause the aiosmtplib client to hang, resulting in a possible denial of service
- inject multiple commands in one address to send an arbitrary message
The address only needs to reach mail()/rcpt()/vrfy()/expn(); no attacker control over the SMTP server is required.
Vulnerable versions
Affected version: aiosmtplib 5.1.0 (latest at time of report) and all earlier releases.
Credit
Reported by tonghuaroot.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | aiosmtplib | all versions | 5.1.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for aiosmtplib. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update aiosmtplib to 5.1.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-v3q9-hj7j-63hq is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-v3q9-hj7j-63hq is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-v3q9-hj7j-63hq. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-v3q9-hj7j-63hq in your dependencies?
O3 detects GHSA-v3q9-hj7j-63hq across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.