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CVE-2026-33540

Distribution server-side request forgery (SSRF)

7.5 HIGHPublic exploitEPSS 0.39%
  1. Published6 Apr 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.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityNone
AvailabilityNone
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Affected products

Distribution< 3.1.0

Remediation

Fixed in
Distribution≥ 3.1.0

References

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Frequently asked

Is CVE-2026-33540 being actively exploited?

CVE-2026-33540 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.39%.

How severe is CVE-2026-33540?

CVE-2026-33540 has a CVSS 3.1 base score of 7.5, rated high. EPSS estimates a 0.39% probability of exploitation.

Which products are affected by CVE-2026-33540?

Affected products include Distribution.

How do I fix CVE-2026-33540?

Upgrade affected software to a fixed version, for example Distribution 3.1.0 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-33540 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.