fflate through 0.8.2 is vulnerable to denial of service via an infinite loop in unzipSync(). A crafted ZIP archive with a central directory entry declaring compressed_size=0xFFFFFFFF (ZIP64 sentinel) but missing the required ZIP64 extra field tag 0x0001 causes z64e() to loop indefinitely due to out-of-bounds reads returning undefined, which coerces to 0, keeping the loop condition permanently true.

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements None

User Interaction None

Vulnerable System Confidentiality Impact None

Vulnerable System Integrity Impact None

Vulnerable System Availability Impact High

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

No CVSS v3.1

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.00255.

Exploitation none

Automatable yes

Technical Impact partial

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
101arrowz fflate unaffected
Version Status Constraints
0.4.5 affected ≤ 0.4.8
0.5.0 affected ≤ 0.5.3
0.6.0 affected ≤ 0.6.10
0.7.0 affected ≤ 0.7.4
0.8.0 affected ≤ 0.8.2

No data.

No data.

No data.

Project Subscriptions

No data.

Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://github.com/101arrowz/fflate/blob/f7873560ad229c22c4b23b06c6a3806ffde77569/src/index.ts#L2714 cve-icon
https://www.npmjs.com/package/fflate cve-icon
History

Wed, 22 Jul 2026 13:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Wed, 22 Jul 2026 07:30:00 +0000

Type Values Removed Values Added
Description fflate through 0.8.2 is vulnerable to denial of service via an infinite loop in unzipSync(). A crafted ZIP archive with a central directory entry declaring compressed_size=0xFFFFFFFF (ZIP64 sentinel) but missing the required ZIP64 extra field tag 0x0001 causes z64e() to loop indefinitely due to out-of-bounds reads returning undefined, which coerces to 0, keeping the loop condition permanently true.
Weaknesses CWE-400
CWE-835
References
Metrics cvssV4_0

{'score': 6.6, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/S:N/AU:Y/R:U/V:D/RE:M/U:Amber'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: seal

Published:

Updated: 2026-07-22T12:53:38.246Z

Reserved: 2026-05-13T12:03:13.544Z

Link: CVE-2026-45820

cve-icon Vulnrichment

Updated: 2026-07-22T12:53:34.532Z

cve-icon NVD

No data.

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses