CVE-2026-46431
Published:May 26, 2026
Updated:June 11, 2026
Algernon is a small self-contained pure-Go web server. Prior to 1.17.7, the SSE event server's Access-Control-Allow-Origin response header was hardcoded to the wildcard * regardless of the caller's Origin. Because EventSource does not preflight and does not send cookies, the wildcard is sufficient to let any third-party page the developer visits open a cross-origin EventSource to the SSE port and read the live filename stream from JavaScript. This vulnerability is fixed in 1.17.7.
Affected Packages
https://github.com/xyproto/algernon.git (GITHUB):
Affected version(s) >=v0.47-win8-64 <v1.17.7Fix Suggestion:
Update to version v1.17.7github.com/xyproto/algernon (GO):
Affected version(s) >=v0.0.0-20150310223114-90791373f0db <v1.17.7Fix Suggestion:
Update to version v1.17.7Related Resources (3)
Do you need more information?
Contact UsCVSS v4
Base Score:
5.3
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
PASSIVE
Vulnerable System Confidentiality
LOW
Vulnerable System Integrity
NONE
Vulnerable System Availability
NONE
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
4.3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
LOW
Integrity
NONE
Availability
NONE
Weakness Type (CWE)
Permissive Cross-domain Security Policy with Untrusted Domains
EPSS
Base Score:
0.03