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vulnerability / NVI-00017527 / Revision 1

flyto-core has SSRF guard bypass via IPv6 transition addresses (IPv4-mapped / 6to4 / NAT64) in validate_url_ssrf

GitHub lists this reviewed advisory for flyto-core. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.

source listedactiveGHSA-794r-5rp2-fpg8CVE-2026-55787

This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.

01 / Meaning

Why it matters

Published affected context helps an owner decide what evidence to gather. This report has not examined your application.

CVSS

7.1 high

GitHub source severity; exploitability and local consequence require separate evidence.

As of · GitHub Advisory Database

02 / Applicability

The affected context

Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.

flyto-core

source listed
  • <= 2.26.2

## Summary `flyto-core`'s SSRF protection (`validate_url_ssrf` / `is_private_ip` in `src/core/utils.py`) blocks private and metadata destinations by resolving the host and testing the resulting IP for membership in a hardcoded `PRIVATE_IP_RANGES` list. That list contains only the *native* RFC 1918 / loopback / link-local / unique-local ranges. It does **not** account for IPv6 transition address forms that embed an IPv4 (or loopback) target: - IPv4-mapped `::ffff:a.b.c.d` - IPv4-compatible `::a.b.c.d` - 6to4 `2002::/16` - NAT64 well-known prefix `64:ff9b::/96` and local-use `64:ff9b:1::/48` A workflow author can submit a URL with a literal transition-form host (for example `http://[::ffff:127.0.0.1]:8080/...` or `http://[64:ff9b::a9fe:a9fe]/latest/meta-data/`). `is_private_ip()` returns `False` for these (the address is not literally inside any listed range), so `validate_url_ssrf` lets the request through, and the `http.get` atomic module (and ~10 sibling modules that share the same guard) performs the outbound `aiohttp` fetch and returns the response body. On a host that uses NAT64/6to4 these addresses route to the embedded IPv4 endpoint (e.g. the cloud instance-metadata servic

GitHub Advisory Database

03 / Response

What to do next

  1. investigate

    Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.

    Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database

A fixed release is not deployment evidence.

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04 / Limits

What this report cannot establish

  • Customer inventory, deployment, reachability and exploitation have not been inspected.
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05 / Provenance

Sources you can inspect

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  1. GHSA-794r-5rp2-fpg8 ↗

    GitHub Advisory Database · vendor advisory

    Observed . GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.

Public revision history

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  1. Revision 1 ·

    First indexed by Null; source disclosure date is shown separately.

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The next step is private

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