PT-2026-42208 · Algernon · Algernon

Dredsen · Published 2026-05-20 · Updated 2026-05-26 · CVE-2026-46431

Positive Technologies (AI Summary)

CVSS v3.1

4.3

Medium

Base vector

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

Name of the Vulnerable Software and Affected Versions Algernon versions prior to 1.17.7

Description The SSE event server's Access-Control-Allow-Origin response header is hardcoded to the wildcard *, regardless of the caller's Origin. Because EventSource does not perform a preflight request and does not send cookies, this configuration allows any third-party page visited by a user to open a cross-origin EventSource connection to the SSE port. This enables a cross-origin script to read the live filename stream from JavaScript. The issue is rooted in the GenFileChangeEvents() function, where the wildcard is passed as the allowed origin, granting script-level read access to the stream for any origin.

Recommendations Update to version 1.17.7. As a temporary workaround, restrict access to the SSE port to minimize the risk of cross-origin exploitation.

Exploit

Fix

Weakness Enumeration

CWE-942

Related Identifiers

CVE-2026-46431

GHSA-HW27-4V2Q-5QFF

Affected Products

Algernon

References · 5

• 🔥 https://github.com/xyproto/algernon/security/advisories/GHSA-hw27-4v2q-5qff · Exploit
• https://nvd.nist.gov/vuln/detail/CVE-2026-46431 · Security Note
• https://osv.dev/vulnerability/GHSA-hw27-4v2q-5qff · Vendor Advisory
• https://github.com/xyproto/algernon · Note
• https://reddit.com/r/VulnMatter/comments/1tjljj9/resumen_diario_de_vulnerabilidades_21052026 · Reddit Post