CVE-2026-46431 json
Algernon: Auto-refresh SSE event server sets Access-Control-Allow-Origin: *
published 2026-05-20 5 mo ago modified 2026-07-24 3 mo ago also EUVD-2026-31870 , GHSA-hw27-4v2q-5qff , GO-2026-5440
- cvss
- 4.3
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.2%
- EPSS 0.2% chance of exploitation in 30 days, percentile 12%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- go github.com/xyproto/algernon 1.17.7
- algernon_project algernon 1.17.7
- govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1
opensuse advisories openSUSE-SU-2026:21483-1
CISA SSVC
- Exploitation
- Proof of concept is public
- Automatable
- no
- Technical impact
- partial
- Assessed
- 5 mo ago
Exploit prediction
0.22% chance of exploitation in the next 30 days, higher than 12% of all scored CVEs (FIRST EPSS, 2026-11-08).
Exploits and checks
- github.com https://github.com/xyproto/algernon/security/advisories/GHSA-hw27-4v2q-5qff referenced PoC, tagged "exploit" by a source, unverified
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 4.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N |
| GitHub | 3.1 | 4.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| go | github.com/xyproto/algernon | <1.17.7 |
1.17.7 |
Affected products
- xyproto algernon
Classification
- Weakness
-
- CWE-942 Permissive Cross-domain Security Policy with Untrusted Domains
References
-
github.com
/xyproto/algernon/security/advisories/GHSA-hw27-4v2q-5qff
exploit, web, advisory
-
nvd.nist.gov
/vuln/detail/CVE-2026-46431
advisory
-
github.com
/xyproto/algernon
package
Sources
- CVE List CVE-2026-46431
- GitHub Advisory GHSA-hw27-4v2q-5qff
- NVD CVE-2026-46431
- OSV GO-2026-5440
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.
CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.