CVE-2026-59873: node-tar: Decompression/parse DoS via unlimited input

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
• EPSS 0.6%, percentile 47: FIRST’s model estimates a 0.6% chance of exploitation activity in the next 30 days, higher than 47% of all scored CVEs (low). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Only applies if your dependency tree includes tar (npm) <= 7.5.18, fixed in 7.5.19. Check your lockfile, including transitive dependencies.

What it is

node-tar is a tar archive manipulation library for Node.js. Prior to 7.5.19, node-tar does not enforce hard upper bounds on total decompressed data, entry counts, or decompression ratio in extraction and parsing paths such as src/extract.ts, allowing a small crafted gzip bomb to exhaust disk space and CPU. This issue is fixed in version 7.5.19.

From the GitHub advisory

Summary A Decompression/parse DoS via unlimited input vulnerability in node-tar allows an attacker to exhaust server resources (disk space and CPU). Because the library does not enforce hard upper bounds on total decompressed data or entry counts, a small, maliciously crafted "Gzip Bomb" can be used to fill a server's storage and crash services.

Details The node-tar library does not enforce a hard upper bound on archive size or the volume of decompressed data processed during extraction. While the maxReadSize option exists, it only controls internal read chunk sizes (default 16MB) and does not limit the total cumulative bytes written to disk.

Specifically, in src/extract.ts, the Unpack stream processes entries as they arrive. There is no total-bytes limit, entry-count limit, or decompression ratio guard. An attacker can provide a TAR header claiming a massive file size (e.g., 10GB) and follow it with highly compressible data (like zeros). node-tar will continue to extract and write this data until the physical disk is exhausted, as it lacks a mechanism to abort based on global resource consumption.

PoC The following Proof of Concept demonstrates how a tiny compressed input can be expanded into gigabytes of data on the host machine almost instantly.

1. Create the exploit script:

Weakness type: CWE-770.

Product: tar (npm) · Assigned by: GitHub_M · Published: 2026-07-08

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Attack requirements: none
• Privileges required: none (no login)
• User interaction: none

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation poc, automatable yes, technical impact partial.
• FIRST EPSS (model of 2026-10-21): 0.58% probability of exploitation activity in the next 30 days; percentile 47.

Timeline

• 2026-07-08 — CVE record last updated
• 2026-07-08 — CVE record published by GitHub_M
• 2026-07-20 — GitHub-reviewed advisory GHSA-23hp-3jrh-7fpw published (critical)

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-23hp-3jrh-7fpw github.com
2. CVE.org record CVE-2026-59873 cve.org
3. NVD entry CVE-2026-59873 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. github.com github.com

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