CVE-2026-45820

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.

We have discovered 87 live websites that are affected by CVE-2026-45820.

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Affected Software

Product  fflate
Category JavaScript Libraries
Vulnerable Domains87 live websites (100% of fflate install base)
Vulnerable Versions
  • from 0.4.5 through 0.4.8
  • from 0.5 through 0.5.3
  • from 0.6 through 0.6.10
  • from 0.7 through 0.7.4
  • from 0.8 through 0.8.2
Vulnerable Versions Count5 versions ( 100% of all versions)


Common Weakness Enumeration

CWE-835 Loop with Unreachable Exit Condition ('Infinite Loop')



Details

  • Published - Jul 22, 2026
  • Updated - Jul 22, 2026

Credits

  • Seal Security (finder)

Website Distribution by Country

Number of websites using CVE-2026-45820
United States61 websites


Russia4 websites
Germany3 websites
Australia2 websites
China2 websites
GB2 websites
Austria1 websites
Brazil1 websites
Canada1 websites

Website Distribution by TLD

Number of websites using CVE-2026-45820
.com39 websites
.net17 websites
.ru4 websites
.at2 websites
.com.au2 websites
.de2 websites
.ca1 websites
.co1 websites
.com.br1 websites
.es1 websites

Vulnerable Versions

Vulnerable versions are highlighted in red

Websites affected by CVE-2026-45820

Top websites that are affected by CVE-2026-45820. Please click on the "Contact us" link to get more information.
DomainCountryRankContacts
*********.com United States***,***
*********.com United States***,***
***.co United States*,***,***
**********.de Germany*,***,***
*************.com United States*,***,***
**********.com United States*,***,***
***.*********.com China*,***,***
*****.*****.info Taiwan*,***,***
******.site United States*,***,***
*******.com India*,***,***
See full domain list

FAQ

CVE-2026-45820 is Loop with Unreachable Exit Condition ('Infinite Loop') in fflate
A total of 87 websites have been identified as vulnerable to CVE-2026-45820, based on global website indexing conducted by WebTechSurvey.
The fflate is affected by the CVE-2026-45820 vulnerability.
fflate versions up to and including 0.8.2 are vulnerable to CVE-2026-45820.