# CVE-2026-127030: FreeRADIUS stack buffer overflow in EAP-FAST module

Source: https://junglewise.ai/threats/cve-2026-127030-a-flaw-was-found-in-freeradius-an-improper-length-validation-in  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-12. Updated: 2026-11-12  
License: CC BY 4.0 with a link back

CVE-2026-127030 · Severity: high · CVSS 7.5 · Published 2026-11-12

FreeRADIUS is an open-source authentication server that handles network access credentials for enterprise systems. An improper length check in the optional EAP-FAST authentication method allows an attacker without credentials to crash the server by sending a malicious network request, causing the authentication service to become unavailable. This affects organizations that have explicitly enabled EAP-FAST, which is not the default configuration.

Technologies: [Freeradius](https://junglewise.ai/threats/technologies/freeradius). Vendors: [Freeradius](https://junglewise.ai/threats/vendors/freeradius).

## Quick answers

**Is CVE-2026-127030 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-127030 being exploited in the wild.

**How severe is CVE-2026-127030?** High severity, with a CVSS score of 7.5, published 12 November 2026.

**Which products and versions are affected?** FreeRADIUS FreeRADIUS.

**Is there a fix for CVE-2026-127030?** No fixed version is recorded yet. Disable the EAP-FAST submodule by commenting out the `fast` section in `/etc/raddb/mods-available/eap` and ensuring `default_eap_type` is not set to `fast`, then restart the radiusd service. Alternatively, restrict UDP port 1812 to only trusted Network Access Server clients using firewall rules. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-127030 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-127030?** Check whether you run Freeradius. 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.

## How to fix


Disable the EAP-FAST submodule by commenting out the `fast` section in `/etc/raddb/mods-available/eap` and ensuring `default_eap_type` is not set to `fast`, then restart the radiusd service. Alternatively, restrict UDP port 1812 to only trusted Network Access Server clients using firewall rules.

## Technical details

A stack-based buffer overflow exists in the EAP-FAST module due to insufficient validation of session ticket length during handshake processing. An unauthenticated remote attacker can send a specially crafted RADIUS packet to trigger the overflow and crash the server process, resulting in denial of service. The vulnerability is rated CWE-787 (out-of-bounds write) and requires network access but no authentication or user interaction.

## Affected products

- FreeRADIUS FreeRADIUS

## Timeline

- 2026-11-12: disclosed

## References

- [https://access.redhat.com/downloads/content/package-browser/](https://access.redhat.com/downloads/content/package-browser/)
- [https://access.redhat.com/security/cve/CVE-2026-127030](https://access.redhat.com/security/cve/CVE-2026-127030)

## Related threats

- [FreeRADIUS stack buffer overflow in EAP-SIM module](https://junglewise.ai/threats/cve-2026-127029-a-flaw-was-found-in-freeradius-s-extensible-authentication)
- [RADIUS Protocol MD5 collision forgery attack (Blast-RADIUS)](https://junglewise.ai/threats/cve-2024-3596-radius-protocol-md5-collision-forgery-attack-blast-radius)