PT-2026-63328 · 101Arrowz · Fflate

Seal Security · CVE-2026-45820 · Published 2026-07-22 · Updated 2026-07-22

NVD

CVSS v4.0

6.6

Medium

Base vector

AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:N/AU:Y/R:U/V:D/RE:M/U:Amber

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.

Fix

Resource Exhaustion

Infinite Loop

Weakness Enumeration

CWE-400

CWE-835

Related Identifiers

CVE-2026-45820

Affected Products

Fflate

References · 3

• https://nvd.nist.gov/vuln/detail/CVE-2026-45820 · Security Note
• https://github.com/101arrowz/fflate/blob/f7873560ad229c22c4b23b06c6a3806ffde77569/src/index.ts#L2714 · Note
• https://npmjs.com/package/fflate · Note