Attack Chain

1. An unauthenticated attacker crafts a small, highly compressed archive, commonly referred to as a "Gzip Bomb".
2. This malicious archive includes a TAR header that falsely claims an extremely large file size for its contents (e.g., 10 gigabytes).
3. The actual content of the archive consists of highly compressible data, such as repeating null bytes.
4. A vulnerable application using the node-tar library (version 7.5.18 or earlier) attempts to extract this attacker-supplied archive.
5. The node-tar Unpack stream processes the archive without enforcing any global limits on the total decompressed data size or the number of entries.
6. The library continuously writes the expanded, highly compressible data to the target system's disk, leading to rapid consumption of all available storage space.
7. The target system's disk resources are exhausted, causing critical applications and services to crash, resulting in a complete Denial of Service.

Impact

This vulnerability poses a critical Denial of Service (DoS) threat. Any application or service that utilizes node-tar (npm/tar) to extract archives from untrusted sources is susceptible. This could include crucial infrastructure like npm registries, CI/CD pipelines, or file-sharing platforms. An unauthenticated attacker can, with a minuscule input, trigger the rapid exhaustion of all available disk space and CPU resources on the target system. This leads to system instability, crashes, and widespread service outages, preventing legitimate users from accessing critical services and significantly disrupting operations.

Recommendation

• Patch CVE-2026-59873 by updating the npm/tar package to a version greater than 7.5.18 immediately.
• Implement resource limits, such as disk quotas and process memory limits, on systems that process untrusted archives to mitigate the impact of resource exhaustion attacks.
• Monitor disk space utilization and CPU load on servers processing user-supplied archives to detect and respond to abnormal resource consumption patterns.