CVE-2026-39971: Serendipity has a Host Header Injection allows SMTP header injection via unvalidated HTTP_HOST in Message-ID email header

high Affects s9y/serendipity. Feed 2026.10.29.3, updated 2026-10-29; published 2026-04-14; advisory modified 2026-05-05.

Serendipity has a Host Header Injection allows SMTP header injection via unvalidated HTTP_HOST in Message-ID email header

Package: s9y/serendipity Composer
Affected versions: <2.6.0
Fixed in: 2.6.0
Severity: high CVSS 7.2
Exploitation: not on CISA KEV · EPSS 0% (17.1th percentile)
Published: 2026-04-14
Source: osv.dev

References

CWE-113

NVD record s9y/serendipity advisories

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