Executive brief
UnrealIRCd is a popular open-source software used to run Internet Relay Chat (IRC) networks. A security flaw in its authentication module allows remote attackers to impersonate other users by spoofing digital certificate fingerprints. If an attacker knows a target user's certificate fingerprint, they can bypass security checks and gain full access to that user's account and associated privileges.
Technical details
A vulnerability exists in the m_authenticate function within modules/m_sasl.c of UnrealIRCd. The software fails to properly validate the AUTHENTICATE parameter, allowing an attacker to inject a spoofed SSL certificate fingerprint into the SASL exchange. By crafting a message containing specific characters (such as a colon or space) in the parameter, an attacker can trick the IRC daemon and backend services into accepting a fraudulent identity. This allows for unauthorized login as any user whose certificate fingerprint is known to the attacker, provided the target user has SASL EXTERNAL authentication enabled. The issue is resolved in versions 3.2.10.7 and 4.0.6.
Affected products
- UnrealIRCd UnrealIRCd 3.2.x before 3.2.10.7, 4.x before 4.0.6
Timeline
- 2016-09-05: advisory: Vendor advisory and CVE assignment confirmed via mailing list
- 2016-09-05: patched: Fix committed to UnrealIRCd repository
- 2017-01-18: disclosed: NVD publication date