# CVE-2026-43915: Coturn stored XSS in web-admin interface via TURN username

Source: https://junglewise.ai/threats/cve-2026-43915-coturn-stored-xss-in-web-admin-interface-via-turn-username  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-18. Updated: 2026-06-21  
License: CC BY 4.0 with a link back

CVE-2026-43915 · Severity: medium · CVSS 5.4 · Published 2026-06-18

Coturn is an open-source server used for relaying media traffic in VoIP and web communication systems. A security flaw in its web-based administration interface allows an attacker to inject malicious scripts by using a specially crafted username during a connection request. If an administrator views the active session list, these scripts could execute in their browser, potentially allowing the attacker to perform unauthorized actions or steal administrative session information.

Technologies: [Coturn](https://junglewise.ai/threats/technologies/coturn). Vendors: [Coturn](https://junglewise.ai/threats/vendors/coturn).

## Quick answers

**Is CVE-2026-43915 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-43915 being exploited in the wild.

**How severe is CVE-2026-43915?** Medium severity, with a CVSS score of 5.4, published 18 June 2026.

**Which products and versions are affected?** Coturn < 4.11.0.

**Is there a fix for CVE-2026-43915?** A patch was published on 2026-05-08: Version 4.11.0 released Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-43915 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-43915?** Check whether you run Coturn at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A stored cross-site scripting (XSS) vulnerability exists in the Coturn web-admin interface due to improper neutralization of the USERNAME value. The root cause involves insufficient input validation in 'is_secure_string()' (which fails to filter '<', '>', and '&') and a lack of HTML entity encoding when rendering the username in the session list ('/ps') within 'turn_admin_server.c'. An attacker can exploit this by creating a TURN allocation with a malicious payload in the username field. In deployments using '--no-auth', no credentials are required; otherwise, valid TURN credentials are needed. Successful exploitation allows execution of arbitrary JavaScript in the context of an authenticated administrator's session. The issue is fixed in version 4.11.0.

## Affected products

- coturn coturn < 4.11.0

## Timeline

- 2026-05-24: advisory: GitHub Security Advisory published
- 2026-05-08: patched: Version 4.11.0 released
- 2026-06-18: disclosed: CVE published to NVD

## References

- [https://github.com/coturn/coturn/releases/tag/4.11.0](https://github.com/coturn/coturn/releases/tag/4.11.0)
- [https://github.com/coturn/coturn/security/advisories/GHSA-xxf5-9vj2-g84j](https://github.com/coturn/coturn/security/advisories/GHSA-xxf5-9vj2-g84j)

## Related threats

- [Coturn quota bypass in mobility-enabled allocations](https://junglewise.ai/threats/cve-2026-73216-coturn-quota-bypass-in-mobility-enabled-allocations)
- [Coturn EVEN-PORT relay port exhaustion](https://junglewise.ai/threats/cve-2026-73215-coturn-even-port-relay-port-exhaustion)
- [Coturn DTLS memory exhaustion via fragmented ClientHello](https://junglewise.ai/threats/cve-2026-73214-coturn-dtls-memory-exhaustion-via-fragmented-clienthello)
- [Coturn IPv6 range check bypass in TURN relay](https://junglewise.ai/threats/cve-2026-73213-coturn-ipv6-range-check-bypass-in-turn-relay)
- [Coturn TURN/STUN relay ACL bypass via IPv6 address encoding](https://junglewise.ai/threats/cve-2026-73212-coturn-turn-stun-relay-acl-bypass-via-ipv6-address-encoding)