---
id: GHSA-6c87-g9pw-78fx
title: >-
  Contrast's Imagepuller registryFor uses unanchored suffix matching, leaking
  auth credentials and trusted CA configuration to sibling-domain registries
summary: >-
  Contrast's Imagepuller registryFor uses unanchored suffix matching, leaking
  auth credentials and trusted CA configuration to sibling-domain registries
severity: low
cvss: 3.7
cwe:
  - CWE-1289
vendor: edgelesssys
product: github.com/edgelesssys/contrast
ecosystem: go
affected:
  - github.com/edgelesssys/contrast <= 1.20.0
patched:
  - github.com/edgelesssys/contrast 1.21.0
published: '2026-07-01'
updated: '2026-07-01'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-6c87-g9pw-78fx'
references:
  - url: >-
      https://github.com/edgelesssys/contrast/security/advisories/GHSA-6c87-g9pw-78fx
  - url: >-
      https://github.com/edgelesssys/contrast/commit/10826b1d82613025767fb094e8aa51a7dcfbd2a1
  - url: 'https://github.com/edgelesssys/contrast/releases/tag/v1.21.0'
  - url: 'https://github.com/advisories/GHSA-6c87-g9pw-78fx'
tags:
  - ghsa
  - go
ingestedAt: '2026-07-01T19:15:59.913Z'
---

## Overview

# Summary

`Config.registryFor` selected a per-registry credential / CA / mirror block by checking `strings.HasSuffix(name, fqdn)` after stripping a single trailing dot. 
The match has no boundary between the configured FQDN and any preceding characters in the request hostname.
A registry configured as `[registries."ghcr.io."]` is therefore also applied to any image pulled from a host whose name happens to end in the literal byte sequence `ghcr.io`, 
including attacker-registered domains such as `evilghcr.io.` 
The imagepuller would then send the configured `Authorization` header (basic auth, registry token, or identity token), trust the configured custom CA bundle,
follow the configured mirror, or honour `insecure-skip-verify`, on requests to that hostname.

# Prerequisites

For this to be applicable, an image or layer must be pulled from a "sibling" domain ending in one of the FQDNs configured in the imagepuller config.
This may occur due to malicious intent or coincidentally.

# Impact

- Authentication header leaks to the sibling registry.
- If `insecure-skip-verify` is set on an FQDN, TLS will also not be verified for the sibling registry.
- Mirrors configured for an FQDN will also be used with the sibling registry.

## Not impacted

Image integrity is **not** impacted. Image bytes remain pinned by digest in the policy and are validated after the pull.
This advisory does not allow code substitution.

# Workaround

- If possible, configure explicit subdomains in the imagepuller config. A configuration for `[registries.".example.registry"]` is unaffected, only `[registries."example.registry"]` is potentially affected.
- Audit images and layers configured in the deployment for the existence of sibling domains.

# Patches

After this patch, registry matches are determined by exact label equality instead of suffix matching.
Each `.`-separated part of the FQDN must be an exact match with the corresponding label in the image reference.

# Severity

- `AV:N` because the leak is over the network to a registry under the attacker's control. 
- `AC:H` because exploitation requires the operator to have configured a registry FQDN without a leading `.` AND the attacker to control a sibling-suffix domain that the deployment will pull from.
- `PR:N` for the eventual recipient. 
- `S:U` because impact stays in the imagepuller. 
- `C:L` for credential leak (no integrity / availability impact).

## Affected packages

- `github.com/edgelesssys/contrast <= 1.20.0`

## Remediation

Upgrade to a patched release:

- `github.com/edgelesssys/contrast 1.21.0`