CVE-2026-33540

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{"affected": [{"affectedData": [{"product": "distribution", "vendor": "distribution", "versions": [{"status": "affected", "version": "< 3.1.0"}]}], "source": "security-advisories@github.com"}], "configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:distribution_project:distribution:*:*:*:*:*:go:*:*", "matchCriteriaId": "A9736C6D-CC89-49C4-BF90-C1E5F31A82B0", "versionEndExcluding": "3.1.0", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "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."}], "id": "CVE-2026-33540", "lastModified": "2026-06-17T10:37:40.780", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 7.5, "baseSeverity": "HIGH", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 3.6, "source": "security-advisories@github.com", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-33540", "options": [{"exploitation": "poc"}, {"automatable": "yes"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-04-06T15:04:46.763761Z", "version": "2.0.3"}}]}, "published": "2026-04-06T15:17:10.950", "references": [{"source": "security-advisories@github.com", "tags": ["Exploit", "Mitigation", "Vendor Advisory"], "url": "https://github.com/distribution/distribution/security/advisories/GHSA-3p65-76g6-3w7r"}, {"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "tags": ["Exploit", "Mitigation", "Vendor Advisory"], "url": "https://github.com/distribution/distribution/security/advisories/GHSA-3p65-76g6-3w7r"}], "sourceIdentifier": "security-advisories@github.com", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-918"}], "source": "security-advisories@github.com", "type": "Secondary"}]}

{"bugzilla": {"description": "github.com/distribution/distribution: Distribution: Information disclosure via improper validation of authentication realm URL", "id": "2455430", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2455430"}, "csaw": false, "cvss3": {"cvss3_base_score": "3.1", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N", "status": "draft"}, "cwe": "CWE-918", "details": ["A flaw was found in Distribution, a toolkit for managing container content. When operating in pull-through cache mode, Distribution incorrectly processes authentication challenges from an upstream registry. An attacker controlling the upstream registry, or positioned as a Man-in-the-Middle (MitM), can exploit this by providing a malicious authentication realm URL. This vulnerability can cause Distribution to send sensitive upstream credentials, via basic authentication, to an attacker-controlled server, leading to information disclosure."], "mitigation": {"lang": "en:us", "value": "To mitigate this issue, ensure that all upstream registries configured for Distribution in pull-through cache mode are trusted and secured. Implement network segmentation and firewall rules to restrict outbound connections from the Distribution instance to only known and trusted upstream registry endpoints. This reduces the risk of an attacker-controlled upstream or a Man-in-the-Middle attack redirecting authentication."}, "name": "CVE-2026-33540", "package_state": [{"cpe": "cpe:/a:redhat:openshift:4", "fix_state": "Fix deferred", "package_name": "openshift3/ose-operator-lifecycle-manager", "product_name": "Red Hat OpenShift Container Platform 4"}, {"cpe": "cpe:/a:redhat:openshift:4", "fix_state": "Fix deferred", "package_name": "openshift4/ose-operator-framework-tools-rhel9", "product_name": "Red Hat OpenShift Container Platform 4"}, {"cpe": "cpe:/a:redhat:openshift:4", "fix_state": "Fix deferred", "package_name": "openshift4/ose-operator-lifecycle-manager", "product_name": "Red Hat OpenShift Container Platform 4"}, {"cpe": "cpe:/a:redhat:openshift:4", "fix_state": "Fix deferred", "package_name": "openshift4/ose-operator-lifecycle-manager-rhel9", "product_name": "Red Hat OpenShift Container Platform 4"}, {"cpe": "cpe:/a:redhat:openshift:4", "fix_state": "Fix deferred", "package_name": "openshift4/ose-operator-registry", "product_name": "Red Hat OpenShift Container Platform 4"}, {"cpe": "cpe:/a:redhat:openshift:4", "fix_state": "Fix deferred", "package_name": "redhat/redhat-operator-index", "product_name": "Red Hat OpenShift Container Platform 4"}], "public_date": "2026-04-06T14:55:04Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-33540\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-33540\nhttps://github.com/distribution/distribution/security/advisories/GHSA-3p65-76g6-3w7r"], "threat_severity": "Moderate"}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0,3.1.0)"}}], "enrichment": {"confidence": 100.0, "confidence_source": "cna", "scores": [{"score": 100.0, "source": "cna"}]}, "original": {"product": "distribution", "source": "cna", "vendor": "distribution"}, "product": "distribution", "vendor": "distribution"}], "analysis": {"en": {"generated_at": "2026-04-09T19:53:17.772794+00:00", "value": {"mitigation_remediation": ["Upgrade Distribution to version\u202f3.1.0 or later.", "If an upgrade is not possible, verify that any configured upstream registry\u2019s bearer challenge realm matches the expected host and does not redirect to a third\u2011party URL.", "Implement network segmentation or firewall rules that restrict Distribution\u2019s outbound traffic to known upstream registry hosts.", "Monitor logs for unexpected outbound HTTP requests to unfamiliar realms, which may indicate an attempt to exfiltrate credentials."], "summary": {"action": "Immediate Patch", "impact": "Credential Exfiltration via Unvalidated Bearer Realm"}, "threat_synthesis": {"affected_systems": "All releases of Distribution before version\u202f3.1.0 that enable pull\u2011through caching are affected. The issue occurs when the upstream registry presents a bearer challenge and the realm component is taken at face value.", "description_and_impact": "Distribution is a toolkit for shipping container content that retrieves authentication token endpoints from upstream registries by parsing WWW\u2011Authenticate challenges. The bearer challenge contains a realm URL, which Distribution uses to obtain access tokens without verifying that the realm matches the intended upstream host. This weakness, identified as CWE\u2011918, means an attacker who can control or intercept the upstream registry\u2019s challenge can supply a malicious realm URL. Distribution will then send the configured upstream credentials by basic authentication to the attacker\u2011controlled endpoint, revealing credentials that can be used to pull private images or impersonate the upstream registry.", "risk_and_exploitability": "The CVSS score is 7.5, indicating high severity, while the EPSS score is below 1\u202f%, suggesting that exploitation is not currently common and the vulnerability is not listed in CISA\u2019s KEV catalog. The likely attack vector is network\u2011based, requiring the attacker to control the upstream registry or position themselves as a man\u2011in\u2011the\u2011middle to inject a rogue challenge. Successful exploitation results in credential exfiltration, allowing unauthorized access to downstream registry resources."}}}}, "created": "2026-04-06T20:14:18.136552+00:00", "updated": "2026-04-10T09:45:16.474496+00:00", "vendors": ["distribution", "distribution$PRODUCT$distribution"]}