Homebox generic notifier SSRF via HTTP redirect after URL validation

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

HomeBox is a home inventory and organization system. Prior to version 0.27.0, Homebox validates generic notifier URLs with ValidateNotifierURL before creation, update, testing, and scheduled delivery, but shoutrrr sends the request through http.DefaultClient.Do without a CheckRedirect policy that revalidates each Location target. An authenticated collection member can configure a permitted notifier host that redirects to loopback, link-local, cloud metadata, or another blocked destination, causing the follow-up request to bypass the product's SSRF policy. The flaw is reachable through POST /api/v1/notifiers/test for immediate requests and through stored notifiers during scheduled maintenance delivery. This issue is fixed in version 0.27.0.

Source published

27 Oct 2026 17:43:52 UTC

Source modified

27 Oct 2026 17:43:52 UTC

Observed here

27 Oct 2026 18:43:43 UTC

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CVSS 3.1 · 6.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N