# CVE-2026-122146: 101arrowz fflate index.mjs unzipSync memory allocation


- **Severity:** Medium 6.9 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P`)
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 5 Nov 2026
- **Updated:** 10 Nov 2026
- **Also known as:** GHSA-3xf2-c6c2-98qc

## What is CVE-2026-122146?

CVE-2026-122146 is a medium-severity vulnerability in 101arrowz fflate, published on 5 Nov 2026. 

### Official description

A weakness has been identified in 101arrowz fflate up to 0.8.3. This issue affects the function unzipSync of the file esm/index.mjs. This manipulation causes uncontrolled memory allocation. It is possible to initiate the attack remotely. The exploit has been made available to the public and could be used for attacks. It is suggested to update the configuration settings. The maintainer disputes this issue as a vulnerability. The library is a pure JavaScript decompressor that allocates memory proportional to the decompressed payload size, which is expected behavior. Excessive allocations simply throw a standard JavaScript RangeError or reach engine heap limits. Furthermore, because a low-level decompression library cannot distinguish between a maliciously crafted compression bomb and a legitimate file with a high compression ratio, the API explicitly provides a filter option allowing callers to restrict decompressed file sizes and prevent denial-of-service according to their application's requirements, as seen both in the documentation and noted in the reported issue.

Weakness: CWE-789 (Memory Allocation with Excessive Size Value), CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2026-122146?


## How do I fix CVE-2026-122146?

No fix has been published for CVE-2026-122146 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-122146 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-122146 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-122146 and fix it if it is affected.

What it is: CVE-2026-122146 is a medium-severity vulnerability in 101arrowz fflate, published on 5 Nov 2026. 
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-122146 exists.

Affected product: 101arrowz fflate. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-122146/ (Markdown: https://insights.sbomify.com/CVE-2026-122146/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-122146
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-122146
- OSV: https://osv.dev/vulnerability/CVE-2026-122146

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-122146/
Summaries are generated and may contain mistakes; the official description above is the record.