Application hang via malformed ZIP64 metadata
Published Jul 22, 2026 · Updated Jul 22, 2026
Denial of service in 101arrowz fflate through 0.8.2 allows remote attackers to hang applications by processing a crafted ZIP archive. In unzipSync(), z64e() scans beyond a central-directory entry when the ZIP64 size sentinel lacks extra-field tag 0x0001; undefined bytes become zero, so the loop never exits. An application must pass attacker-supplied ZIP data to unzipSync(), after which the affected process hangs without reported data disclosure or modification.
Summary
What happened
Denial of service in 101arrowz fflate through 0.8.2 allows remote attackers to hang applications by processing a crafted ZIP archive. In unzipSync(), z64e() scans beyond a central-directory entry when the ZIP64 size sentinel lacks extra-field tag 0x0001; undefined bytes become zero, so the loop never exits. An application must pass attacker-supplied ZIP data to unzipSync(), after which the affected process hangs without reported data disclosure or modification.
The record
- CVE
- CVE-2026-45820
- Published
- Jul 22, 2026
- Updated
- Jul 22, 2026
- Vendor
- 101arrowz
- Product
- fflate
- Classifications
- CWE-400, CWE-835, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 22, 2026CVE publishedPublication date reported by the CVE source.
- Jul 22, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=0.4.5 <=0.4.8
- Affected versionversion=0.5.0 <=0.5.3
- Affected versionversion=0.6.0 <=0.6.10
- Affected versionversion=0.7.0 <=0.7.4
- Affected versionversion=0.8.0 <=0.8.2
What conditions does exploitation require?
What is affected?
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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