Bug 2572340 (CVE-2026-127030)

Summary: CVE-2026-127030 freeradius: Stack buffer overflow via unchecked EAP-FAST SessionTicket length
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: rhel-process-autobot, security-response-team, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in freeradius. An improper length validation in the EAP-FAST module allows a stack-based buffer overflow during session ticket processing. A remote, unauthenticated attacker can exploit this flaw by sending a specially crafted handshake request, causing the server process to crash and resulting in a Denial of Service (DoS).
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Bug Depends On: 2572354    
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Description OSIDB Bzimport 2026-11-12 11:35:19 UTC 
A flaw was found in freeradius's EAP-FAST module. The SessionTicket callback invoked during the TLS ClientHello phase of the EAP-FAST handshake validates the PAC-Opaque length using mismatched integer types, allowing an attacker-supplied value to underflow and bypass the check. The callback then decrypts attacker-controlled ciphertext into a fixed-size buffer before the authentication tag is verified, so a crafted ClientHello can write data past the end of a stack buffer. A remote, unauthenticated client speaking EAP-FAST to a server with the module enabled can trigger this to crash the RADIUS server process before any credential exchange.