# CVE-2026-53450: Coturn: IPv4-mapped 127.0.0.1 bypasses default loopback peer protection

> An authenticated attacker can bypass loopback protection to access localhost services via IPv4-mapped IPv6 addresses in TURN relay traffic.

- **Severity:** High 7.4 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 10 Jul 2026
- **Updated:** 10 Jul 2026
- **Also known as:** DEBIAN-CVE-2026-53450, GHSA-w4hf-cr3w-6h79, UBUNTU-CVE-2026-53450

## What is CVE-2026-53450?

CVE-2026-53450 is a high-severity server-side request forgery vulnerability in coturn, published on 10 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Coturn is a free open source implementation of TURN and STUN Server. Prior to 4.13.0, coturn rejects loopback peers by default unless allow-loopback-peers is enabled, but the default loopback guard can be bypassed by using the IPv4-mapped IPv6 peer address ::ffff:127.0.0.1 in a TURN XOR-PEER-ADDRESS attribute. ioa_addr_is_loopback checks for the literal IPv6 loopback shape before IPv4-mapped IPv6 handling, so good_peer_addr does not apply the default loopback rejection and an authenticated TURN client can expose services bound only to localhost on the coturn host through TURN relay traffic. This issue is fixed in version 4.13.0.

Weakness: CWE-918 (Server-Side Request Forgery)

## Which versions are affected by CVE-2026-53450?

It affects 1 product.


Products: Coturn Project Coturn.

## How do I fix CVE-2026-53450?

Upgrade to a fixed version.

## Is CVE-2026-53450 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-53450 exists.

## Other vulnerabilities in coturn

- [CVE-2018-4056](https://insights.sbomify.com/CVE-2018-4056/): SQL injection in coTURN (critical 9.1)
- [CVE-2026-43994](https://insights.sbomify.com/CVE-2026-43994/): Coturn: Stack buffer overflow in decode_oauth_token_gcm() (high 8.1)
- [CVE-2018-4058](https://insights.sbomify.com/CVE-2018-4058/): Server-side request forgery in coTURN (high 7.7)
- [CVE-2026-40613](https://insights.sbomify.com/CVE-2026-40613/): Coturn: Misaligned Memory Access in coturn STUN Attribute Parser (Remote DoS on ARM64) (high 7.5)
- [CVE-2026-53448](https://insights.sbomify.com/CVE-2026-53448/): Coturn: SQL Injection in HTTPS Admin Panel Delete Operations (high 7.2)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-53450 and fix it if it is affected.

What it is: CVE-2026-53450 is a high-severity server-side request forgery vulnerability in coturn, published on 10 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-53450 exists.

Affected product: coturn. 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-2026-53450/ (Markdown: https://insights.sbomify.com/CVE-2026-53450/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53450
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53450
- OSV: https://osv.dev/vulnerability/CVE-2026-53450

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-53450/
Summaries are generated and may contain mistakes; the official description above is the record.