CVE-2026-27890: Firebird has Pre-Auth DOS when Processing Out of Order CNCT_specific_data Segments
Firebird is an open-source relational database management system. In versions prior to 5.0.4, 4.0.7 and 3.0.14, when processing CNCTspecificdata segments during authentication, the server assumes segments arrive in strictly ascending order. If segments arrive out of order, the Array class's grow() method computes a negative size value, causing a SIGSEGV crash. An unauthenticated attacker who knows only the server's IP and port can exploit this to crash the server. This issue has been fixed in versions 5.0.4, 4.0.7 and 3.0.14.
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-27890?
CVE-2026-27890 has been classified as a high severity vulnerability due to its potential to cause Denial of Service (DoS) during the authentication process.
How do I fix CVE-2026-27890?
To mitigate CVE-2026-27890, update your Firebird installation to version 5.0.4 or later, or 4.0.7 or later, or 3.0.14 or later.
What versions of Firebird are affected by CVE-2026-27890?
CVE-2026-27890 affects Firebird versions prior to 5.0.4, 4.0.7, and 3.0.14.
What type of attack does CVE-2026-27890 allow?
CVE-2026-27890 allows for a Pre-Auth Denial of Service (DoS) attack by processing CNCT_specific_data segments out of order.
Is authentication affected by CVE-2026-27890?
Yes, CVE-2026-27890 affects the authentication process of Firebird by impacting the way it processes CNCT_specific_data segments.