# CVE-2026-33540: docker-registry: Distribution is a toolkit to pack, ship, store, and deliver container content

CVE-2026-33540 is fixed in 3 products on 1 platform, first by DEBIAN-CVE-2026-33540, released April 6, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-33540
- Priority: High
- CVSS: 7.5 (high)
- EPSS: 0.0029
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Apr 6, 2026

## Description

Distribution is a toolkit to pack, ship, store, and deliver container content. Prior to 3.1.0, in pull-through cache mode, distribution discovers token auth endpoints by parsing WWW-Authenticate challenges returned by the configured upstream registry. The realm URL from a bearer challenge is used without validating that it matches the upstream registry host. As a result, an attacker-controlled upstream (or an attacker with MitM position to the upstream) can cause distribution to send the configured upstream credentials via basic auth to an attacker-controlled realm URL. This vulnerability is fixed in 3.1.0.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | distribution sles 15.6 | 3.1.1-150400.9.41.1 | [SUSE-SU-2026:4212-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4212-1.md) | Sep 16, 2026 |
| Linux | distribution sles 15.7 | 3.1.1-150400.9.41.1 | [SUSE-SU-2026:4212-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4212-1.md) | Sep 16, 2026 |
| Linux | docker-registry Debian 14 | 2.8.3+ds1-3 | [DEBIAN-CVE-2026-33540](https://patchblox.com/security/data/fix/linux/debian-cve-2026-33540.md) | Apr 6, 2026 |
| Linux | govulncheck-vulndb opensuse-leap 16.0 | 0.0.20260723T184607-160000.1.1 | [OPENSUSE-SU-2026:21483-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21483-1.md) | Jul 30, 2026 |

---

Data as of 2026-11-08T13:06:02Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

Free to use with attribution: show "Data: Patchblox Patch Radar" with a link to https://patchblox.com/security/patch-radar. Terms, including what needs a written agreement: https://patchblox.com/security/patch-radar/use-the-data

Product names, logos and trademarks shown on Patch Radar belong to their respective owners. They are used only to identify the software each security fix applies to and to help readers find their platform. Their use does not imply any affiliation with, or endorsement by, those owners, and Patchblox is not affiliated with any of them.