# CVE-2026-39805: CL.CL HTTP request smuggling via duplicate Content-Length in bandit

> An attacker can smuggle HTTP requests past security controls by exploiting inconsistent Content-Length header handling in the Bandit server.

- **Severity:** Medium 6.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/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:** Yes
- **Published:** 1 May 2026
- **Updated:** 24 Jul 2026
- **Also known as:** EEF-CVE-2026-39805, GHSA-c67r-gc9j-2qf7

## What is CVE-2026-39805?

CVE-2026-39805 is a medium-severity vulnerability in mtrudel bandit, published on 1 May 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 vulnerability in mtrudel bandit allows HTTP request smuggling via duplicate Content-Length headers.

'Elixir.Bandit.Headers':get_content_length/1 in lib/bandit/headers.ex uses List.keyfind/3, which returns only the first matching header. When a request contains two Content-Length headers with different values, Bandit silently accepts it, uses the first value to read the body, and dispatches the remaining bytes as a second pipelined request on the same keep-alive connection. RFC 9112 §6.3 requires recipients to treat this as an unrecoverable framing error.

When Bandit sits behind a proxy that picks the last Content-Length value and forwards the request rather than rejecting it, an unauthenticated attacker can smuggle requests past edge WAF rules, path-based ACLs, rate limiting, and audit logging.

This issue affects bandit: before 1.11.0.

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

## Which versions are affected by CVE-2026-39805?

3 open source packages ship an affected version, including bandit.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `bandit` | Hex | All versions | 1.11.0 |
| `bandit` | Hex | All versions | 1.11.0 |
| `bandit` | Hex | From 0.1.0 | 1.11.0 |

## How do I fix CVE-2026-39805?

Upgrade bandit to 1.11.0 or later.

## Is CVE-2026-39805 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-39805 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-39805 and fix it if it is affected.

What it is: CVE-2026-39805 is a medium-severity vulnerability in mtrudel bandit, published on 1 May 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-2026-39805 exists.

Affected packages and fixed versions:
- bandit (Hex): affected all versions; fixed in 1.11.0
- bandit (Hex): affected all versions; fixed in 1.11.0
- bandit (Hex): affected from 0.1.0; fixed in 1.11.0

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-2026-39805/ (Markdown: https://insights.sbomify.com/CVE-2026-39805/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-39805
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-39805
- OSV: https://osv.dev/vulnerability/CVE-2026-39805

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-39805/
Summaries are generated and may contain mistakes; the official description above is the record.