101arrowz fflate up to 0.8.2 Zip64 src/index.ts unzipSync infinite loop

Summaryinfo

A vulnerability, which was classified as problematic, was found in 101arrowz fflate up to 0.4.8/0.5.3/0.6.10/0.7.4/0.8.2. Affected by this vulnerability is the function unzipSync of the file src/index.ts of the component Zip64 Handler. The manipulation results in infinite loop. This vulnerability is reported as CVE-2026-45820. The attack can be launched remotely. No exploit exists.

Detailsinfo

A vulnerability was found in 101arrowz fflate up to 0.4.8/0.5.3/0.6.10/0.7.4/0.8.2. It has been classified as problematic. Affected is the function unzipSync of the file src/index.ts of the component Zip64 Handler. The manipulation with an unknown input leads to a infinite loop vulnerability. CWE is classifying the issue as CWE-835. The product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop. This is going to have an impact on availability. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-45820 since 05/13/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1499.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-47616). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Productinfo

Vendor

• 101arrowz

Name

• fflate

Version

• 0.4.0
• 0.4.1
• 0.4.2
• 0.4.3
• 0.4.4
• 0.4.5
• 0.4.6
• 0.4.7
• 0.4.8
• 0.5.0
• 0.5.1
• 0.5.2
• 0.5.3
• 0.6.0
• 0.6.1
• 0.6.2
• 0.6.3
• 0.6.4
• 0.6.5
• 0.6.6
• 0.6.7
• 0.6.8
• 0.6.9
• 0.6.10
• 0.7.0
• 0.7.1
• 0.7.2
• 0.7.3
• 0.7.4
• 0.8.0
• 0.8.1
• 0.8.2

Website

• Product: https://github.com/101arrowz/fflate/

CPE 2.3info

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CPE 2.2info

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VulDB is the best source for vulnerability data and more expert information about this specific topic.

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