CVE-2026-27890Public exploitNetwork attack vector

Unauthenticated server crash via out-of-order authentication segments

Published Apr 17, 2026 · Updated Apr 17, 2026

Out-of-bounds write in Firebird 3.x before 3.0.14, 4.x before 4.0.7, and 5.x before 5.0.4 allows remote attackers to crash the server. During authentication, the CNCT_specific_data reassembly path passes a lower out-of-order sequence offset to Array::grow(), which derives an invalid fill length and makes memset trigger SIGSEGV. Only the server IP and port are required; no credentials or user interaction are needed, and successful exploitation terminates the database service.

CVSS severity8.2
High
EPSS probability0.46%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds write in Firebird 3.x before 3.0.14, 4.x before 4.0.7, and 5.x before 5.0.4 allows remote attackers to crash the server. During authentication, the CNCT_specific_data reassembly path passes a lower out-of-order sequence offset to Array::grow(), which derives an invalid fill length and makes memset trigger SIGSEGV. Only the server IP and port are required; no credentials or user interaction are needed, and successful exploitation terminates the database service.

The record

CVE
CVE-2026-27890
Published
Apr 17, 2026
Updated
Apr 17, 2026
Vendor
Firebird Project
Product
Firebird
Classifications
CWE-787, CWE-119, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 17, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 17, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 3.0.0, < 3.0.14
  2. Affected versionversion=>= 4.0.0, < 4.0.7
  3. Affected versionversion=>= 5.0.0, < 5.0.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Firebird Project · Firebirdversion=>= 3.0.0, < 3.0.14; version=>= 4.0.0, < 4.0.7; version=>= 5.0.0, < 5.0.4

Published CVSS scores

8.2GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-787Out-of-bounds Write
CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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