# CVE-2026-40606: ProxyAuth Addon LDAP Injection in mitmproxy

> Attackers can bypass authentication in mitmproxy's LDAP proxy auth feature by injecting malicious LDAP queries via unsanitized usernames.

- **Severity:** Medium 4.8 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 21 Apr 2026
- **Updated:** 22 Apr 2026
- **Also known as:** DEBIAN-CVE-2026-40606, GHSA-527g-3w9m-29hv, PYSEC-2026-92, UBUNTU-CVE-2026-40606, openSUSE-SU-2026:10622-1

## What is CVE-2026-40606?

CVE-2026-40606 is a medium-severity authentication bypass vulnerability in mitmproxy, published on 21 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

mitmproxy is a interactive TLS-capable intercepting HTTP proxy for penetration testers and software developers and mitmweb is a web-based interface for mitmproxy. In mitmproxy 12.2.1 and below, the builtin LDAP proxy authentication does not correctly sanitize the username when querying the LDAP server. This allows a malicious client to bypass authentication. Only mitmproxy instances using the proxyauth option with LDAP are affected. This option is not enabled by default. The vulnerability has been fixed in mitmproxy 12.2.2 and above.

Weakness: CWE-90 (Improper Neutralization of Special Elements used in an LDAP Query)

## Which versions are affected by CVE-2026-40606?

3 open source packages ship an affected version, including mitmproxy. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `mitmproxy` | PyPI | All versions | 12.2.2 |
| `mitmproxy` | PyPI | All versions | 12.2.2 |
| `mitmproxy` | PyPI | All versions | 12.2.2 |
| `python-mitmproxy` | openSUSE:Tumbleweed | All versions | 12.2.2-1.1 |

Products: Mitmproxy Mitmproxy.

## How do I fix CVE-2026-40606?

Upgrade mitmproxy to 12.2.2 or later.

## Is CVE-2026-40606 being exploited?

There is no known exploitation of CVE-2026-40606 in the wild and no public exploit code.

## Other vulnerabilities in mitmproxy

- [CVE-2022-24766](https://insights.sbomify.com/CVE-2022-24766/): Insufficient Protection against HTTP Request Smuggling in mitmproxy (critical 9.8)
- [CVE-2018-14505](https://insights.sbomify.com/CVE-2018-14505/): Mitmweb in mitmproxy allows DNS Rebinding attacks (high 8.8)
- [CVE-2021-39214](https://insights.sbomify.com/CVE-2021-39214/): Lacking Protection against HTTP Request Smuggling in mitmproxy (high 8.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-40606 and fix it if it is affected.

What it is: CVE-2026-40606 is a medium-severity authentication bypass vulnerability in mitmproxy, published on 21 Apr 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-2026-40606 in the wild and no public exploit code.

Affected packages and fixed versions:
- mitmproxy (PyPI): affected all versions; fixed in 12.2.2
- mitmproxy (PyPI): affected all versions; fixed in 12.2.2
- mitmproxy (PyPI): affected all versions; fixed in 12.2.2

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-2026-40606/ (Markdown: https://insights.sbomify.com/CVE-2026-40606/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-40606
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40606
- OSV: https://osv.dev/vulnerability/CVE-2026-40606

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-40606/
Summaries are generated and may contain mistakes; the official description above is the record.