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High, CVSS 8.7amended

Bifrost's SSRF deny-list is incomplete: isPublicIP permits CGNAT, IPv6 6to4/NAT64, and site-local in FetchAndEncodeURL

CVE-2026-55245GHSA-w98g-5w9p-p3rc

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (github.com/maximhq/bifrost/core 1.5.17), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
8.7 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N · score source
EPSS
  • CVE-2026-55245: 0.61% estimated exploitation activity in the next 30 days; percentile 49.29 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Summary isPublicIP in core/providers/utils/fetch.go — the SSRF deny-list that gates FetchAndEncodeURL — does not reject several routable address ranges that map onto internal infrastructure. Carrier-Grade NAT (100.64.0.0/10, RFC 6598), IPv6 6to4 (2002::/16), NAT64 (64:ff9b::/96 and 64:ff9b:1::/48), and deprecated IPv6 site-local (fec0::/10) are all classified as public and permitted. An attacker who controls a multimodal image/document URL in a Bedrock or Vertex request body can drive the gateway to fetch internal services it should not reach — including the cloud instance-metadata endpoint via the 6to4 / NAT64 embeddings of 169.254.169.254. The rest of the fetch hardening is correct and is not part of this report: the dial-time LookupIP + pin to ips[0] closes the DNS-rebinding TOCTOU, CheckRedirect re-validates redirect targets, the scheme gate, the 25 MiB cap, and the 20 s timeout all work. This is purely a residual IP-classification gap in isPublicIP. Affected component - File:…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 4 · amended ·

    Amended from ghsa record GHSA-w98g-5w9p-p3rc

  2. Revision 3 · amended ·

    Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

  3. Revision 2 · amended ·

    Amended from osv record GO-2026-6320

  4. Revision 1 · created ·

    Published from osv record GHSA-w98g-5w9p-p3rc

Agent brief

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# Patch Next advisory brief: CVE-2026-55245

Advisory: Bifrost's SSRF deny-list is incomplete: isPublicIP permits CGNAT, IPv6 6to4/NAT64, and site-local in FetchAndEncodeURL
IDs: CVE-2026-55245, GHSA-w98g-5w9p-p3rc
Record: https://patchnext.com/advisories/cve-2026-55245 (revision 4, source checked 26 Oct 2026, 15:28 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/maximhq/bifrost/core 1.5.17. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/maximhq/bifrost/core: affected < 1.5.17; fixed in 1.5.17

## Suggested inspection (read-only)
- Go github.com/maximhq/bifrost/core: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/maximhq/bifrost/core.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-w98g-5w9p-p3rc (OSV record GHSA-w98g-5w9p-p3rc lists affected ranges: Go github.com/maximhq/bifrost/core >=0 <1.5.17 (fixed))
- Verified: https://osv.dev/vulnerability/GO-2026-6320 (OSV record GO-2026-6320 lists affected ranges: Go github.com/maximhq/bifrost/core >=0 <1.5.17 (fixed))
- Verified: https://github.com/advisories/GHSA-w98g-5w9p-p3rc (GitHub-reviewed advisory GHSA-w98g-5w9p-p3rc lists affected ranges: Go github.com/maximhq/bifrost/core >=0 <1.5.17)

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