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CVE-2026-46431

MEDIUMCVSS 4.3/10EPSS 0.22%

Last modified

CVE-2026-46431 is a medium-severity vulnerability rated 4.3/10 on the CVSS scale. 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. EPSS estimates a 0.22% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1
4.3/10

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

EPSS Probability
0.22%

12.3th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

References

Timeline

Published
Last Modified
Status
Deferred

Frequently Asked Questions

What is CVE-2026-46431?
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.
How severe is CVE-2026-46431?
CVE-2026-46431 has a CVSS score of 4.3/10 (MEDIUM severity). The EPSS model estimates a 0.22% probability of exploitation in the next 30 days.
How do I fix CVE-2026-46431?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-46431?

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Source: NVD / NIST