What is the CVSS score of CVE-2026-22903?

CVE-2026-22903 has a CVSS 3.1 base score of 9.8 (Critical). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 0.6%.

How to fix or mitigate CVE-2026-22903?

Within 24 hours: Inventory all lighttpd deployments and assess exposure to untrusted networks; implement emergency WAF rules to block oversized SESSIONID cookies. Within 7 days: Deploy network segmentation to restrict direct internet access to affected servers and monitor for exploitation attempts. Within 30 days: Evaluate lighttpd alternatives or contact vendor for patch availability; implement stack canaries and memory protections where possible; conduct security assessment of affected systems.

CVE-2026-22903

CRITICAL

Stack-based Buffer Overflow (CWE-121)

2026-02-09 info@cert.vde.com

RCE Buffer Overflow Denial Of Service

9.8

CVSS 3.1 · NVD

Severity by source

NVD PRIMARY

9.8 CRITICAL

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

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

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

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

Analysis Generated

Mar 12, 2026 - 21:54 vuln.today

CVE Published

Feb 09, 2026 - 08:16 nvd

CRITICAL 9.8

DescriptionCVE.org

An unauthenticated remote attacker can send a crafted HTTP request containing an overly long SESSIONID cookie. This can trigger a stack buffer overflow in the modified lighttpd server, causing it to crash and potentially enabling remote code execution due to missing stack protections.