GHSA-4vj7-5mj6-jm8m
MEDIUMmorgan vulnerable to Log Forging via unneutralized control characters in :remote-user
Blast Radius
Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.
morgannpmDescription
Impact
Morgan's :remote-user token extracts the Basic auth username from the Authorization header and writes it to the log stream without neutralizing control characters. An attacker can send a crafted Authorization: Basic header containing CR/LF characters to inject forged log lines, corrupting the one-request-per-line structure of access logs.
The built-in combined, common, default, and short formats are affected, as well as any custom format that includes :remote-user.
Patches
Users should upgrade to version 1.11.0.
Workarounds
Use a custom format string that does not include :remote-user.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | morgan | ≥ 1.2.0&&< 1.11.0 | 1.11.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for morgan. 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 morgan to 1.11.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-4vj7-5mj6-jm8m 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-4vj7-5mj6-jm8m 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-4vj7-5mj6-jm8m. 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-4vj7-5mj6-jm8m in your dependencies?
O3 detects GHSA-4vj7-5mj6-jm8m across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.