High [CVE-2026-39246] arbitrary symlink creation during archive extraction leads to information disclosure
This high-severity Red Hat Linux advisory covers CVE-2026-39246 affecting Red Hat Advanced Cluster Management for Kubernetes 2, Red Hat Build of Keycloak.
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Summary
decompress before 4.2.2 allows arbitrary symlink creation during archive extraction. When processing symlink entries (type === 'symlink'), the x.linkname field from the archive is passed directly to fs.symlink() without validation (index.js line 121).
The preventWritingThroughSymlink check on line 98 only applies to file entries, not symlink creation. An attacker can craft an archive with symlink entries pointing to sensitive files outside the extraction directory (e.g., /etc/passwd), enabling information disclosure when the application reads the extracted contents.
A flaw was found in the decompress package for Node.js. The package creates symlinks from archive entries during extraction without validating the link target against the output directory, because the existing containment check only applies to regular file entries.
An attacker who can supply a crafted archive for extraction (for example a malicious package tarball or user-uploaded archive) can create a symlink inside the output directory that points to an arbitrary path such as /etc/passwd.
If the extracting application subsequently reads or serves the extracted files, the attacker can achieve disclosure of any file readable by the extracting process, and in combination with a later write to the same symlinked path, potentially write through the link as well.
- < 4.2.2
Official advisory · high-confidence parse· fetched 10 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 10 days ago·verify at source
Mitigation checklist
- Do not use decompress to extract archives from untrusted sources. Where extraction of externally-supplied or otherwise untrusted archives is required, migrate to the maintained fork @xhmikosr/decompress (>= 10.2.1 or >= 11.1.3), which validates symlink and hardlink targets against the output directory before creating them. As an interim mitigation, run extraction as a non-privileged, sandboxed process and reject any archive containing symlink or hardlink entries before extraction.
Official advisory · high-confidence parse· fetched 10 days ago·verify at source
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