# CVE-2026-23941: Request smuggling via first-wins Content-Length parsing in inets httpd

> Attackers can exploit HTTP request smuggling in Erlang OTP inets httpd by sending duplicate Content-Length headers, causing desynchronization with reverse proxies.

- **Severity:** High 7.0 (`CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 13 Mar 2026
- **Updated:** 24 Jul 2026
- **Also known as:** AZL-79880, DEBIAN-CVE-2026-23941, EEF-CVE-2026-23941, GHSA-w4jc-9wpv-pqh7, UBUNTU-CVE-2026-23941

## What is CVE-2026-23941?

CVE-2026-23941 is a high-severity vulnerability in Erlang OTP, published on 13 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Inconsistent Interpretation of HTTP Requests ('HTTP Request Smuggling') vulnerability in Erlang OTP (inets httpd module) allows HTTP Request Smuggling.

This vulnerability is associated with program files lib/inets/src/http_server/httpd_request.erl and program routines httpd_request:parse_headers/7.

The server does not reject or normalize duplicate Content-Length headers. The earliest Content-Length in the request is used for body parsing while common reverse proxies (nginx, Apache httpd, Envoy) honor the last Content-Length value. This violates RFC 9112 Section 6.3 and allows front-end/back-end desynchronization, leaving attacker-controlled bytes queued as the start of the next request.

This issue affects OTP from OTP 17.0 before OTP 28.4.1, OTP 27.3.4.9 and OTP 26.2.5.18, corresponding to inets from 5.10 before 9.6.1, 9.3.2.3 and 9.1.0.5.

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

## Which versions are affected by CVE-2026-23941?

It affects 2 products.


Products: Erlang Erlang\/Inets, Erlang Erlang\/Otp.

## How do I fix CVE-2026-23941?

Upgrade to a fixed version.

## Is CVE-2026-23941 being exploited?

There is no known exploitation of CVE-2026-23941 in the wild and no public exploit code.

## Other vulnerabilities in Erlang OTP

- [CVE-2026-28808](https://insights.sbomify.com/CVE-2026-28808/): ScriptAlias CGI targets bypass directory auth in inets httpd (mod_auth vs mod_cgi path mismatch) (high 8.3)
- [CVE-2026-48856](https://insights.sbomify.com/CVE-2026-48856/): httpc leaks Authorization header to cross-origin redirect targets (high 7.1)
- [CVE-2026-48858](https://insights.sbomify.com/CVE-2026-48858/): ftp client PASV response IP not validated against control peer, enabling SSRF and FTP bounce attacks (medium 6.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-23941 and fix it if it is affected.

What it is: CVE-2026-23941 is a high-severity vulnerability in Erlang OTP, published on 13 Mar 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-2026-23941 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-2026-23941/ (Markdown: https://insights.sbomify.com/CVE-2026-23941/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-23941
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-23941
- OSV: https://osv.dev/vulnerability/CVE-2026-23941

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-23941/
Summaries are generated and may contain mistakes; the official description above is the record.