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

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Summary

CVECVE-2026-27890
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-17 19:16:34 UTC
Updated2026-04-24 20:05:41 UTC
DescriptionFirebird 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.

Risk And Classification

Primary CVSS: v3.1 8.2 HIGH from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H

EPSS: 0.000920000 probability, percentile 0.257680000 (date 2026-04-21)

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

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary8.2HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
3.1CNADECLARED8.2HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Firebirdsql Firebird All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA FirebirdSQL Firebird affected >= 3.0.0, < 3.0.14 Not specified
CNA FirebirdSQL Firebird affected >= 4.0.0, < 4.0.7 Not specified
CNA FirebirdSQL Firebird affected >= 5.0.0, < 5.0.4 Not specified

References

ReferenceSourceLinkTags
github.com/FirebirdSQL/firebird/security/advisories/GHSA-6crx-4g37-7j49 [email protected] github.com Exploit, Vendor Advisory
github.com/FirebirdSQL/firebird/releases/tag/v5.0.4 [email protected] github.com Release Notes
github.com/FirebirdSQL/firebird/releases/tag/v4.0.7 [email protected] github.com Release Notes
github.com/FirebirdSQL/firebird/releases/tag/v3.0.14 [email protected] github.com Release Notes
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis
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