CVE-2026-101894 in decompress
Summary
by MITRE • 09/28/2026
The decompress package for Node.js extracts archives. Prior to 10.2.2 and 11.1.4, the default decompress(input, output) API relies on lexical containment checks that do not account for the kernel following a planted symlink chain. An attacker can supply a crafted archive containing chained symlink entries so that a later entry resolves outside the output directory. This allows files outside output to be read or written, and overwriting startup scripts or configuration can lead to remote code execution. The maintained @xhmikosr/decompress package is fixed in 10.2.2 and 11.1.4, but the separately affected unmaintained decompress package remains unpatched through 4.2.1. This vulnerability results from a bypass of the incomplete hardening for CVE-2026-53486. @xhmikosr/decompress is fixed in versions 10.2.2 and 11.1.4.
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Analysis
by VulDB Data Team • 09/28/2026
The decompress package, widely used within Node.js environments to extract archive files such as ZIP or TAR formats, contains a critical path traversal vulnerability that undermines the integrity of file extraction operations. This flaw stems from an incomplete implementation of directory containment checks designed to prevent archives from writing files outside their designated output directories. The core issue lies in how the library validates paths during decompression. Specifically, prior to versions 10.2.2 and 11.1.4 for the maintained @xhmikosr/decompress package, the default API relied on lexical containment checks that failed to account for symbolic link resolution by the underlying operating system kernel. This oversight creates a scenario where an attacker can craft malicious archives containing chained symlink entries. When such an archive is processed, the library may validate the initial path as safe based on its string representation within the output directory. However, once the extraction process follows these symlinks, the actual file location resolved by the kernel can point to arbitrary locations outside the intended sandboxed output folder.
This vulnerability allows for both unauthorized reading and writing of files in directories that should remain inaccessible during normal archive extraction operations. The operational impact is severe because it enables an attacker to overwrite critical system or application files. For instance, if a Node.js application uses decompress to process user-uploaded archives as part of its functionality, an attacker could supply a crafted payload that overwrites startup scripts, configuration files, or other sensitive assets located in parent directories relative to the output path. Such modifications can lead directly to remote code execution, granting the attacker full control over the affected system. This type of attack is particularly dangerous because it bypasses standard security controls intended to isolate untrusted input from critical application resources, effectively turning a utility function into an arbitrary write primitive that compromises the entire host environment.
From a technical classification perspective, this vulnerability aligns with CWE-22: Improper Limitation of a Pathname to a Restricted Directory, commonly known as path traversal or directory traversal. The specific mechanism involving symbolic links places it firmly within the realm of symlink following attacks, which are often exploited when applications do not resolve paths before performing security checks. In terms of offensive cybersecurity frameworks, this behavior maps to ATT&CK technique T1059: Command and Scripting Interpreter if used for execution via overwritten scripts, or more broadly to initial access vectors that leverage file manipulation for persistence or privilege escalation. The root cause is identified as a bypass of incomplete hardening measures originally intended to address CVE-2026-53486, indicating that previous mitigation attempts were insufficient against sophisticated symlink chaining techniques.
The remediation landscape presents a notable challenge due to the existence of two distinct packages with overlapping functionality but different maintenance statuses. The actively maintained @xhmikosr/decompress package has been patched in versions 10.2.2 and 11.1.4, providing a clear upgrade path for projects that depend on this specific fork or namespace. However, the original decompress package remains unmaintained through version 4.2.1 without any available patch. Organizations relying on the older, unpatched package are left vulnerable unless they migrate to the maintained alternative or implement external mitigations such as using a secure extraction library that properly resolves symlinks before validation, restricting file system permissions via sandboxing, or validating archive contents through static analysis prior to decompression. It is imperative for developers to audit their dependencies and ensure that any package handling untrusted archives implements robust path canonicalization checks that resolve all symbolic links against the intended output directory boundary before allowing write operations.