CVE-2026-90668

UnrealIRCd Webserver Header DoS Vulnerability

Published Sep 13, 2026 CVSS 4.0 · 8.7 High EPSS < 1% KEV · Not listed
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).

Remediation

Vendor 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


Vendor Workaround

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

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
Title UnrealIRCd Webserver Header DoS Vulnerability
Type Values Removed Values Added
Title UnrealIRCd Webserver Header Limit Exhaustion Leading to Denial of Service
Type Values Removed Values Added
Metrics ssvc

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

Type Values Removed Values Added
Title UnrealIRCd Webserver Header Limit Exhaustion Leading to Denial of Service
Type Values Removed Values Added
Title UnrealIRCd Webserver Header DoS via Unlimited HTTP Headers
Type Values Removed Values Added
Title UnrealIRCd Webserver Header DoS via Unlimited HTTP Headers
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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
mitre
Published
Updated
Sep 14, 2026, 6:13 PM
Reserved
Sep 13, 2026, 2:00 AM
Status
Deferred
Published
Sep 13, 2026, 2:17 AM
Modified
Sep 22, 2026, 8:00 PM