# CVE-2026-66730: facil.io 0.6.0 - 0.7.6 Infinite Loop DoS via Multipart MIME Body Parser

> An unauthenticated remote attacker can cause a permanent denial of service by sending a malformed multipart request that triggers an infinite loop in the parser.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 27 Jul 2026
- **Updated:** 31 Jul 2026
- **Also known as:** GHSA-gc74-g85r-w7x5

## What is CVE-2026-66730?

CVE-2026-66730 is a high-severity denial of service vulnerability in boazsegev facil.io, published on 27 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

facil.io 0.6.0 through 0.7.6 contains a denial-of-service vulnerability in the multipart body parser that allows an unauthenticated remote attacker to permanently freeze worker processes at 100% CPU by sending a multipart/form-data request with a partial closing boundary. The missing progress guard in the parser loop causes http_mime_parse to return 0 bytes consumed without setting done or error flags, causing the calling loop to re-invoke the parser on the same buffer indefinitely, exhausting all workers and permanently disabling the server until manually restarted.

Weakness: CWE-835 (Loop with Unreachable Exit Condition)

## Which versions are affected by CVE-2026-66730?


## How do I fix CVE-2026-66730?

No fix has been published for CVE-2026-66730 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-66730 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-66730 exists.

Public exploit code:

- Security Advisory: Infinite Loop DoS in facil.io MIME Parser (Partial Boundary) (github_poc): https://github.com/theopaid/CVE-2026-66730-Infinite-Loop-DoS-in-facil.io-MIME-Parser

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-66730 and fix it if it is affected.

What it is: CVE-2026-66730 is a high-severity denial of service vulnerability in boazsegev facil.io, published on 27 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-66730 exists.

Affected product: boazsegev facil.io. 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-2026-66730/ (Markdown: https://insights.sbomify.com/CVE-2026-66730/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-66730
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-66730
- OSV: https://osv.dev/vulnerability/CVE-2026-66730

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-66730/
Summaries are generated and may contain mistakes; the official description above is the record.