The webserver in UnrealIRCd 6.0.5 through 6.2.6 before 6.2.7 does not limit the number of HTTP request headers, which allows remote attackers to cause a denial of service (memory consumption and unresponsive server) via an HTTP request with an unlimited number of headers, if a websocket or JSON-RPC listener is enabled (disabled by default).

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Advisories

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Fixes

Solution

Upgrade to UnrealIRCd 6.2.7 or later. Alternatively, apply the hot-patch to fix the issue without restart: ./unrealircd hot-patch webserver-header-dos


Workaround

Remove the websocket and rpc options from your listen blocks until the patch or upgrade is applied.

History

Tue, 15 Sep 2026 02:30:00 +0000

Type Values Removed Values Added
Title UnrealIRCd Webserver Header Limit Exhaustion Leading to Denial of Service

Mon, 14 Sep 2026 21:00:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Mon, 14 Sep 2026 06:00:00 +0000

Type Values Removed Values Added
Title UnrealIRCd Webserver Header Limit Exhaustion Leading to Denial of Service

Sun, 13 Sep 2026 21:15:00 +0000

Type Values Removed Values Added
Title UnrealIRCd Webserver Header DoS via Unlimited HTTP Headers

Sun, 13 Sep 2026 12:30:00 +0000

Type Values Removed Values Added
Title UnrealIRCd Webserver Header DoS via Unlimited HTTP Headers

Sun, 13 Sep 2026 02:15:00 +0000

Type Values Removed Values Added
Description The webserver in UnrealIRCd 6.0.5 through 6.2.6 before 6.2.7 does not limit the number of HTTP request headers, which allows remote attackers to cause a denial of service (memory consumption and unresponsive server) via an HTTP request with an unlimited number of headers, if a websocket or JSON-RPC listener is enabled (disabled by default).
First Time appeared Unrealircd
Unrealircd unrealircd
Weaknesses CWE-770
CPEs cpe:2.3:a:unrealircd:unrealircd:*:*:*:*:*:*:*:*
Vendors & Products Unrealircd
Unrealircd unrealircd
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

cvssV4_0

{'score': 8.7, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/AU:Y/R:A/RE:L'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: mitre

Published:

Updated: 2026-09-14T18:13:44.948Z

Reserved: 2026-09-13T02:00:53.718Z

Link: CVE-2026-90668

cve-icon Vulnrichment

Updated: 2026-09-14T18:13:36.085Z

cve-icon NVD

Status : Received

Published: 2026-09-13T02:17:05.103

Modified: 2026-09-14T19:18:08.107

Link: CVE-2026-90668

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-15T02:15:12Z

Weaknesses