CVE-2026-45820
fflate Denial of Service Vulnerability
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.
INFO
Published Date :
July 22, 2026, 8:16 a.m.
Last Modified :
July 22, 2026, 8:16 a.m.
Remotely Exploit :
Yes !
Source :
22e2d327-25fe-45d7-9f0c-dcd23b7108df
Affected Products
The following products are affected by CVE-2026-45820
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 4.0 | MEDIUM | 22e2d327-25fe-45d7-9f0c-dcd23b7108df | ||||
| CVSS 4.0 | MEDIUM | 22e2d327-25fe-45d7-9f0c-dcd23b7108df |
Solution
- Update fflate to the latest version.
- Apply vendor patches if available.
- Validate ZIP archive integrity.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-45820.
| URL | Resource |
|---|---|
| https://github.com/101arrowz/fflate/blob/f7873560ad229c22c4b23b06c6a3806ffde77569/src/index.ts#L2714 | |
| https://www.npmjs.com/package/fflate |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-45820 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-45820
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-45820 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-45820 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by 22e2d327-25fe-45d7-9f0c-dcd23b7108df
Jul. 22, 2026
Action Type Old Value New Value Added Affected [{'vendor': '101arrowz', 'product': 'fflate', 'versions': [{'status': 'affected', 'version': '0.4.5', 'versionType': 'semver', 'lessThanOrEqual': '0.4.8'}, {'status': 'affected', 'version': '0.5.0', 'versionType': 'semver', 'lessThanOrEqual': '0.5.3'}, {'status': 'affected', 'version': '0.6.0', 'versionType': 'semver', 'lessThanOrEqual': '0.6.10'}, {'status': 'affected', 'version': '0.7.0', 'versionType': 'semver', 'lessThanOrEqual': '0.7.4'}, {'status': 'affected', 'version': '0.8.0', 'versionType': 'semver', 'lessThanOrEqual': '0.8.2'}], 'platforms': ['Linux', 'macOS', 'Windows'], 'defaultStatus': 'unaffected'}] 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. Added CVSS V4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/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 Added CWE CWE-400 Added CWE CWE-835 Added Reference https://github.com/101arrowz/fflate/blob/f7873560ad229c22c4b23b06c6a3806ffde77569/src/index.ts#L2714 Added Reference https://www.npmjs.com/package/fflate