FreeRADIUS: EAP-SIM module stack buffer overflow (CVE-2026-127029)
FreeRADIUS contains a stack buffer overflow vulnerability in its EAP-SIM module, allowing an unauthenticated remote attacker to cause a Denial of Service (DoS) by sending crafted authentication requests.
CVE search metadata
CVE search record: CVE-2026-127029. Severity: high. CVSS: 7.5. KEV: no. Product: FreeRADIUS. Brief: FreeRADIUS: EAP-SIM module stack buffer overflow (CVE-2026-127029). Brief link: https://feed.craftedsignal.io/briefs/2026-11-freeradius-eap-sim-buffer-overflow-cve-2026-127029/
Triage facts
Revision 1- Applicability
- FreeRADIUS
- Evidence
- Unknown
- Severity
- Low
- Action
- Elevated
- Sources
- 1 public source
- Freshness
- Revision 1Nov 12, 18:45 UTC
- Vulnerabilities
- 1 CVE
- Source quality
- A1Likely
A buffer overflow vulnerability exists in the FreeRADIUS Extensible Authentication Protocol Method for Subscriber Identity Module (EAP-SIM) module. The issue arises when the server processes authentication requests and fails to validate the length of a client-supplied identity string before copying it into a fixed-size internal buffer. An unauthenticated attacker can exploit this flaw to crash the FreeRADIUS service.
Impact
Successful exploitation results in a Denial of Service (DoS) of the FreeRADIUS service. The vulnerability carries a CVSS v3.1 base score of 7.5.
Recommendation
- Identify all instances of FreeRADIUS within the environment.
- Monitor vendor security advisories for the release of a patched version of FreeRADIUS.
- Implement network-level rate limiting or authentication inspection to identify anomalous EAP-SIM traffic patterns directed at the RADIUS server.
Immediate actions
Audit network to identify and inventory all deployments of FreeRADIUS.
Threat Hunt
Investigate RADIUS server logs for unexpected service crashes, restarts, or segmentation faults following high volumes of EAP-SIM authentication requests.
Data: RADIUS service logs, OS system logs (e.g., /var/log/syslog, dmesg)