compliance-trestle has an URLSecurityValidator SSRF allowlist bypass via IPv4-mapped IPv6 and 0.0.0.0

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

8.6 · CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-52776: 0.44% estimated exploitation activity in the next 30 days; percentile 38.21 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary compliance-trestle 4.0.3 (latest) ships an URLSecurityValidator in trestle/core/remote/security.py to block SSRF to loopback / link-local / cloud-metadata endpoints from the HTTPSFetcher and SFTPFetcher remote-fetch paths. The allowlist is incomplete and can be bypassed by four equivalent address representations that resolve to the same blocked host but evade the validator's checks: - IPv4-mapped IPv6 literals ([::ffff:169.254.169.254], [::ffff:127.0.0.1], [::ffff:10.0.0.1]) are returned by socket.getaddrinfo as IPv6Address objects; IPv6Address in IPv4Network('169.254.0.0/16') returns False, so the checkblockednetworks and checkprivatenetworks predicates do not match. - IPv4 unspecified address 0.0.0.0 is not in ALWAYSBLOCKEDNETWORKS (which covers 127.0.0.0/8 but not 0.0.0.0/8); on Linux + Docker, 0.0.0.0 routes to local services on any interface, and on dual-stack-mapped sockets it also reaches loopback listeners. A malicious OSCAL profile referencing one of these URLs in…

Published by the source

12 Aug 2026, 15:21 UTC

Last modified by the source

12 Aug 2026, 15:21 UTC

Source last checked

26 Oct 2026, 13:50 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-h47f-gmjp-m7rr

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# Patch Next advisory brief: CVE-2026-52776

Advisory: compliance-trestle has an URLSecurityValidator SSRF allowlist bypass via IPv4-mapped IPv6 and 0.0.0.0
IDs: CVE-2026-52776, GHSA-h47f-gmjp-m7rr
Record: https://patchnext.com/advisories/cve-2026-52776 (revision 1, source checked 26 Oct 2026, 13:50 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.6)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: compliance-trestle 4.1.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI compliance-trestle: affected < 4.1.0; fixed in 4.1.0

## Suggested inspection (read-only)
- `python -m pip show compliance-trestle`: prints the installed version. Run with the environment that serves production active.

## 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 compliance-trestle.
- 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://github.com/advisories/GHSA-h47f-gmjp-m7rr (GitHub-reviewed advisory GHSA-h47f-gmjp-m7rr lists affected ranges: PyPI compliance-trestle >=0 <4.1.0)

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