Out-of-bounds write in Firebird - CVE-2026-27890

Vulnerability identifier: #VU126555

CSH Severity: High

CVSS v4: 8.8 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-27890

CWE-ID: CWE-787

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to cause a denial of service.

The vulnerability exists due to an out-of-bounds write in CNCT_specific_data handling when processing out-of-order CNCT_specific_data sequence segments during authentication. A remote attacker can send specially crafted sequence segments to cause a denial of service.

The issue can be triggered before authentication and may cause a SIGSEGV in the server process.

Firebird
SUSE Linux Enterprise Desktop 15
SUSE Linux Enterprise Real Time 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Package Hub 15
firebird
firebird-debugsource
libib_util
firebird-examples
libfbclient2
libib_util-debuginfo
firebird-utils
firebird-server
libib_util-devel
libfbclient2-debuginfo
firebird-server-debuginfo
firebird-utils-debuginfo
libfbclient-devel
firebird-debuginfo

Install security update from vendor's website.

Firebird - addressed in versions 3.0.14, 4.0.7, 5.0.4
firebird - update to 3.0.14.33856-150200.3.9.1
firebird-debugsource - update to 3.0.14.33856-150200.3.9.1
libib_util - update to 3.0.14.33856-150200.3.9.1
firebird-examples - update to 3.0.14.33856-150200.3.9.1
libfbclient2 - update to 3.0.14.33856-150200.3.9.1
libib_util-debuginfo - update to 3.0.14.33856-150200.3.9.1
firebird-utils - update to 3.0.14.33856-150200.3.9.1
firebird-server - update to 3.0.14.33856-150200.3.9.1
libib_util-devel - update to 3.0.14.33856-150200.3.9.1
libfbclient2-debuginfo - update to 3.0.14.33856-150200.3.9.1
firebird-server-debuginfo - update to 3.0.14.33856-150200.3.9.1
firebird-utils-debuginfo - update to 3.0.14.33856-150200.3.9.1
libfbclient-devel - update to 3.0.14.33856-150200.3.9.1
firebird-debuginfo - update to 3.0.14.33856-150200.3.9.1

• https://github.com/FirebirdSQL/firebird/security/advisories/GHSA-6crx-4g37-7j49
• https://github.com/advisories/GHSA-6crx-4g37-7j49

• Multiple vulnerabilities in Firebird
• SUSE update for firebird