What’s Vulnerable › Vulnerabilities

CVE-2026-27890: Firebird has Pre-Auth DOS when Processing Out of Order CNCT_specific_data Segments

• Severity: high (CVSS 8.2 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-04-17 · updated 2026-10-26
• Weakness: CWE-119

Description

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 CNCT_specific_data 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 products

• FirebirdSQL firebird: before 3.0.14; from 4.0.0 before 4.0.7; from 5.0.0 before 5.0.4 — fixed in 3.0.14, 4.0.7, 5.0.4

How to fix

Upgrade to a fixed version: FirebirdSQL firebird 3.0.14, 4.0.7, 5.0.4. Check the vendor advisory for mitigations.

References

• https://github.com/FirebirdSQL/firebird/releases/tag/v3.0.14
• https://github.com/FirebirdSQL/firebird/releases/tag/v4.0.7
• https://github.com/FirebirdSQL/firebird/releases/tag/v5.0.4
• https://github.com/FirebirdSQL/firebird/security/advisories/GHSA-6crx-4g37-7j49

Get alerted when CVE-2026-27890 or the next vulnerability affects your stack