How severe is CVE-2026-33540?

CVE-2026-33540 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2026-33540 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (19th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-33540?

CVE-2026-33540 affects Distribution Project Distribution. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-33540?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-33540 have an EU (EUVD) identifier?

Yes. CVE-2026-33540 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-19289.

When was CVE-2026-33540 published?

CVE-2026-33540 was published on 2026-04-06 and last updated on 2026-06-17.

CVE-2026-33540

CVE-2026-33540 is a high-severity vulnerability in Distribution Project Distribution with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-918.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 0% (19th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-19289
Weakness: CWE-918
Affected product: Distribution Project Distribution
Published: 2026-04-06
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2026-33540?: 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.
How severe is CVE-2026-33540?: CVE-2026-33540 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2026-33540 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (19th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-33540?: CVE-2026-33540 affects Distribution Project Distribution. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-33540?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-33540 have an EU (EUVD) identifier?: Yes. CVE-2026-33540 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-19289.
When was CVE-2026-33540 published?: CVE-2026-33540 was published on 2026-04-06 and last updated on 2026-06-17.

References

https://github.com/distribution/distribution/security/advisories/GHSA-3p65-76g6-3w7r

Affected products (1)

cpe:2.3:a:distribution_project:distribution:*:*:*:*:*:go:*:*

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