CVE-2026-27890

Firebird has Pre-Auth DOS when Processing Out of Order CNCT_specific_data Segments

State: Published
Severity: 8.2 High
Published: Apr 17, 2026
Updated: Apr 17, 2026
Reserved: Feb 24, 2026

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.

Scores

CVSS	Score	Vector	Source
3.1	8.2 High	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H	GitHub_M

Weaknesses

CWE-119 Improper Restriction of Operations within the Bounds of a Memory Buffer
CWE-787 Out-of-bounds Write

Affected Products

Product	Versions
firebirdFirebirdSQL	>= 3.0.0, < 3.0.14Affected >= 4.0.0, < 4.0.7Affected >= 5.0.0, < 5.0.4Affected

References

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