High severity · published Apr 17, 2026
CVE-2026-27890
Firebird has Pre-Auth DOS when Processing Out of Order CNCT_specific_data Segments
8.2
CVSS
0.5%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
Low
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 40% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
FI
firebird · FirebirdSQL
>= 3.0.0, < 3.0.14; >= 4.0.0, < 4.0.7; >= 5.0.0, < 5.0.4 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-27890
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-27890
Release Notes
https://github.com/FirebirdSQL/firebird/releases/tag/v3.0.14
Release Notes
https://github.com/FirebirdSQL/firebird/releases/tag/v4.0.7
Release Notes
https://github.com/FirebirdSQL/firebird/releases/tag/v5.0.4
Exploit
https://github.com/FirebirdSQL/firebird/security/advisories/GHSA-6crx-4g37-7j49
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