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

Exp

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.

Published: 2026-04-17 Last update: 2026-04-24 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-27890 is rated High Exploit Risk (72.3/100): CVSS High severity, with medium exploitation likelihood (EPSS 0.58%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2026-27890

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2026-27890

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-29 0.40% 0.58% +0.19%
2 2026-05-12 0.30% 0.40% +0.10%
3 2026-04-25 — 0.30% —

Full EPSS history (4 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-27890

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.2 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 4.2 [email protected]

Weakness enumeration for CVE-2026-27890

OS Trackers for CVE-2026-27890

vendor priority summary link
debian not yet assigned CVE-2026-27890 not yet assigned priority: Debian including 2 source packages (firebird3.0, firebird4.0), 8 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): open 4, resolved 4. https://security-tracker.debian.org/tracker/CVE-2026-27890
suse high — https://www.suse.com/security/cve/CVE-2026-27890/
ubuntu medium CVE-2026-27890 medium priority: Ubuntu including 2 source packages (firebird3.0, firebird4.0), 12 status rows across 7 suites (bionic, focal, jammy, noble, questing, resolute, upstream): needs-triage 8, DNE 2, released 2. https://ubuntu.com/security/CVE-2026-27890

Affected software / configurations for CVE-2026-27890

Vendor Product Version Raw CPE
firebirdsql firebird < 3.0.14 cpe:2.3:a:firebirdsql:firebird:*:*:*:*:*:*:*:*
firebirdsql firebird >= 4.0.0, < 4.0.7 cpe:2.3:a:firebirdsql:firebird:*:*:*:*:*:*:*:*
firebirdsql firebird >= 5.0.0, < 5.0.4 cpe:2.3:a:firebirdsql:firebird:*:*:*:*:*:*:*:*

References for CVE-2026-27890

cvelogic Threat Intelligence