GHSA-4vj7-5mj6-jm8m
MEDIUMGHSA-4vj7-5mj6-jm8m is a medium-severity (CVSS 5.3) CWE-117 vulnerability in morgan. O3 Security confirms whether GHSA-4vj7-5mj6-jm8m is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
morgan vulnerable to Log Forging via unneutralized control characters in :remote-user
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- 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-4vj7-5mj6-jm8m.
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-4vj7-5mj6-jm8m 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 369,023 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.
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.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
The morgan npm logging middleware is vulnerable to log forgery via unneutralized control characters in the :remote-user token extracted from Basic Authorization headers. A remote unauthenticated attacker can send crafted requests to inject forged log lines, impacting log integrity. Built-in combined, common, default,…
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.