Answer in brief
CVE-2026-45820 records a Medium severity (CVSS 7.5) vulnerability in fflate unzipSync can enter an infinite loop when parsing malformed ZIP64 archives. The current sources do not mark it as known exploited. The current feed maps fflate (npm), fflate (npm), fflate (npm), fflate (npm) and additional mapped packages. Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 7.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps fflate (npm), fflate (npm), fflate (npm), fflate (npm) and additional mapped packages. Check affected ranges and fixed versions before updating.
| Product | Affected versions | Fixed versions |
|---|---|---|
| cpe:2.3:a:101arrowz:fflate:*:*:*:*:*:node.js:*:* | Not reported | Not reported |
| Package | Affected range | Fixed version |
|---|---|---|
| fflatenpm | >=0.5.0,<0.5.4 | 0.5.4 |
| fflatenpm | >=0.6.0,<0.6.11 | 0.6.11 |
| fflatenpm | >=0.7.0,<0.7.5 | 0.7.5 |
| fflatenpm | >=0.8.0,<0.8.3 | 0.8.3 |
| fflatenpm | >=0.4.5,<0.4.9 | 0.4.9 |
Published upstream
Jul 22, 2026
Evidence: source:ghsa:source_dates:source-dates:recordSource modified
Sep 3, 2026
Evidence: source:ghsa:source_dates:source-dates:recordFirst seen by HOL
Aug 20, 2026
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.
Quoted source text, attributed separately from HOL analysis.