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CVE-2026-46431— Algernon: Auto-refresh SSE event server sets Access-Control-Allow-Origin: *

Quick assessment

Affected
xyproto algernon
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

algernon是Alexander F. Rødseth个人开发者的一个 Web 服务器。 algernon 1.17.7之前版本存在安全漏洞，该漏洞源于SSE事件服务器的Access-Control-Allow-Origin响应头硬编码为通配符*，可能导致任意第三方页面跨域读取实时文件名流。

CVSS 4.3 · Medium EPSS 0.22% · P13

Possible ATT&CK Techniques 1 AI

T1059 · Command and Scripting Interpreter

Affected Version Matrix 1

VendorProduct Version RangeStatus
xyproto algernon < 1.17.7 affected
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I. Basic Information for CVE-2026-46431

Vulnerability Information
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Vulnerability Title
Algernon: Auto-refresh SSE event server sets Access-Control-Allow-Origin: *
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
过度许可的跨域白名单
Source: CVE Program / CVE List V5
Vulnerability Title
algernon 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
algernon是Alexander F. Rødseth个人开发者的一个 Web 服务器。 algernon 1.17.7之前版本存在安全漏洞，该漏洞源于SSE事件服务器的Access-Control-Allow-Origin响应头硬编码为通配符*，可能导致任意第三方页面跨域读取实时文件名流。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
xyproto algernon < 1.17.7 -

II. Public POCs for CVE-2026-46431

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III. Intelligence Information for CVE-2026-46431

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Vendor Advisories for CVE-2026-46431 (1)

Same Patch Batch · xyproto · 2026-05-26 · 7 CVEs total

CVE-2026-45721 9.0 CRITICAL Algernon: handler.lua discovery walks parent directories above the server root
CVE-2026-48126 8.2 HIGH Algernon: Host header path traversal in --domain mode reads files and runs Lua from parent
CVE-2026-45728 7.5 HIGH Algernon: Single-file mode unconditionally enables debug mode
CVE-2026-46430 4.3 MEDIUM Algernon: Auto-refresh SSE event server binds to all interfaces by default on Linux/macOS
CVE-2026-43981 Algernon: Race Condition in handle() shared LState
CVE-2026-43982 Algernon: Path traversal file write via savein()

IV. Related Vulnerabilities

Same product: algernon
Same vendor: xyproto
Same weakness: CWE-942

V. Comments for CVE-2026-46431

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