# CVE-2026-66357: inets,httpd:HTTP Request Smuggling via obs-fold Header Continuation

> Attackers can perform HTTP request smuggling against Erlang OTP inets httpd due to missing obs-fold header continuation support, bypassing security controls.

- **Severity:** High 8.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:H/VA:N/SC:N/SI:L/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 1 Sep 2026
- **Updated:** 8 Sep 2026
- **Also known as:** AZL-98460, DEBIAN-CVE-2026-66357, EEF-CVE-2026-66357, GHSA-qh2f-33hj-37qf, UBUNTU-CVE-2026-66357

## What is CVE-2026-66357?

CVE-2026-66357 is a high-severity vulnerability in Erlang OTP, published on 1 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

httpd has never implemented obs-fold (RFC 2616 §2.2 / RFC 7230 §3.2.4 header continuation lines). Every CRLF followed by a non-CRLF octet unconditionally starts a new header. This missing feature became a security concern as the understanding of HTTP request smuggling attacks evolved.

This issue affects OTP from OTP 17.0 before OTP 27.3.4.17, from OTP 28.0 before OTP 28.5.0.6, and from OTP 29.0 before OTP 29.0.6, corresponding to inets from 5.10 before 9.3.2.7, from 9.4 before 9.6.2.3, and from 9.7 before 9.7.2. Whether OTP before OTP 17.0, corresponding to inets before 5.10, is affected is unknown.

Weakness: CWE-444 (Inconsistent Interpretation of HTTP Requests)

## Which versions are affected by CVE-2026-66357?


## How do I fix CVE-2026-66357?

Upgrade to a fixed version.

## Is CVE-2026-66357 being exploited?

There is no known exploitation of CVE-2026-66357 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-66357 and fix it if it is affected.

What it is: CVE-2026-66357 is a high-severity vulnerability in Erlang OTP, published on 1 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-66357 in the wild and no public exploit code.

Affected product: Erlang OTP. 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-2026-66357/ (Markdown: https://insights.sbomify.com/CVE-2026-66357/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-66357
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-66357
- OSV: https://osv.dev/vulnerability/CVE-2026-66357

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-66357/
Summaries are generated and may contain mistakes; the official description above is the record.