The signature verification routine in install.sh in yarnpkg/website through 2018-06-05 only verifies that the yarn release is signed by any (arbitrary) key in the local keyring of the user, and does not pin the signature to the yarn release key, which allows remote attackers to sign tampered yarn release packages with their own key.

In Yarn before 1.21.1, the package install functionality can be abused to generate arbitrary symlinks on the host filesystem by using specially crafted "bin" keys. Existing files could be overwritten depending on the current user permission set.

The package integrity validation in yarn < 1.19.0 contains a TOCTOU vulnerability where the hash is computed before writing a package to cache. It's not computed again when reading from the cache. This may lead to a cache pollution attack.

Yarn before 1.17.3 is vulnerable to Missing Encryption of Sensitive Data due to HTTP URLs in lockfile causing unencrypted authentication data to be sent over the network.

Arbitrary filesystem write vulnerability in Yarn before 1.22.0 allows attackers to write to any path on the filesystem and potentially lead to arbitrary code execution by forcing the user to install a malicious package.

An untrusted search path vulnerability was found in Yarn. When a victim runs certain Yarn commands in a directory with attacker-controlled content, malicious commands could be executed in unexpected ways.

A vulnerability was found in yarnpkg Yarn up to 1.22.22. It has been classified as problematic. Affected is the function explodeHostedGitFragment of the file src/resolvers/exotics/hosted-git-resolver.js. The manipulation leads to inefficient regular expression complexity. It is possible to launch the attack remotely. The patch is identified as 97731871e674bf93bcbf29e9d3258da8685f3076. It is recommended to apply a patch to fix this issue.

A vulnerability has been found in yarnpkg Yarn up to 1.22.22. This impacts the function setOptions of the file src/util/request-manager.js. Such manipulation leads to inefficient regular expression complexity. Local access is required to approach this attack. This vulnerability only affects products that are no longer supported by the maintainer.