GHSA-wm7q-rxch-43mx Byass due to validation before canonicalization in serve
Attackers can bypass file ignore rules to access restricted files or directory listings via URL encoding.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is GHSA-wm7q-rxch-43mx?
GHSA-wm7q-rxch-43mx is a path traversal vulnerability in serve, published on 1 Sep 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Versions of serve before 6.5.2 are vulnerable to the bypass of the ignore functionality. The bypass is possible because validation happens before canonicalization of paths and filenames.
Example: Here we have a server that ignores the file test.txt.
const serve = require('serve')
const server = serve(__dirname, {
port: 1337,
ignore: ['test.txt']
})
Using the URL encoded form of a letter (%65 instead of e) attacker can bypass the ignore control accessing the file.
curl http://localhost:1337/t%65st.txt
Additionally this technique can be used to get directory listings of ignored directories.
Recommendation
Update to version 6.5.2 or later.
Which versions are affected by GHSA-wm7q-rxch-43mx?
2 open source packages ship an affected version, including serve.
| Package | Affected | Fixed in |
|---|---|---|
serve npm | All versions | 6.5.2 |
serve npm | All versions | 6.5.2 |
How do I fix GHSA-wm7q-rxch-43mx?
Upgrade serve to 6.5.2 or later.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is GHSA-wm7q-rxch-43mx being exploited?
There is no known exploitation of GHSA-wm7q-rxch-43mx in the wild and no public exploit code.