{"id":"CVE-2026-122303","kind":"vulnerability","aliases":["CVE-2026-122303"],"related":[],"title":"Kyverno: namespace tenants can overwrite resources in other namespaces","description":"Kyverno from 1.17.0 before 1.19.2 contains an authorization bypass vulnerability that allows namespace tenants to overwrite resources in other namespaces via NamespacedMutatingPolicy mutate-existing targetMatchConstraints.expression. Attackers can return a CEL map literal fabricating a target with an attacker-chosen metadata.namespace, causing the privileged background controller to overwrite Secrets, Deployments, or policies cluster-wide.","summary":"Kyverno versions 1.17.0 through 1.19.1 let a user in one namespace abuse NamespacedMutatingPolicy mutate-existing rules to make the background controller overwrite resources in other namespaces. An attacker can overwrite Secrets, Deployments or policies across the cluster.","severity":"critical","cvss":9.9,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["infrastructure","kubernetes","kyverno","multi-tenant"],"not_affected_if":["kyverno-1.19.2-or-later","kyverno-below-1.17.0","single-tenant-cluster"],"how_to_check":"- Check the Kyverno version with `kubectl get deploy -n kyverno -o wide` or the image tag on the Kyverno controller.\n- Look for NamespacedMutatingPolicy resources using mutate-existing with targetMatchConstraints.expression.","fix":"- Kyverno: move to `1.19.2` or later (affected range is 1.17.0 before 1.19.2).","status":"open","published_at":"2026-11-05T03:17:22+00:00","first_seen_at":"2026-11-05T03:31:40+00:00","triaged_at":"2026-11-05T03:33:06+00:00","updated_at":"2026-11-05T03:33:06+00:00","category":"infrastructure","confidence":0.8,"triage":{"at":"2026-11-05T03:33:06Z","model":"claude-haiku-5-5","output":{"fix":"- Kyverno: move to `1.19.2` or later (affected range is 1.17.0 before 1.19.2).","reach":"network","title":"Kyverno: namespace tenants can overwrite resources in other namespaces","impact":"high","summary":"Kyverno versions 1.17.0 through 1.19.1 let a user in one namespace abuse NamespacedMutatingPolicy mutate-existing rules to make the background controller overwrite resources in other namespaces. An attacker can overwrite Secrets, Deployments or policies across the cluster.","audience":"businesses","category":"infrastructure","nicknames":[],"who_cares":["kubernetes","kyverno","multi-tenant"],"confidence":0.8,"fix_status":"available","needs_auth":"yes","worst_case":"Attacker overwrites cluster Secrets and Deployments in other namespaces","analyst_note":"Confirm the exact policy-creation permission needed and check the GitHub advisory and VulnCheck pages for details on any workaround.","how_to_check":"- Check the Kyverno version with `kubectl get deploy -n kyverno -o wide` or the image tag on the Kyverno controller.\n- Look for NamespacedMutatingPolicy resources using mutate-existing with targetMatchConstraints.expression.","plain_action":"","needs_analyst":true,"not_affected_if":["single-tenant-cluster","kyverno-below-1.17.0","kyverno-1.19.2-or-later"],"who_is_affected":"Clusters running Kyverno from 1.17.0 before 1.19.2 that let namespace tenants create NamespacedMutatingPolicy resources with mutate-existing rules. Single-tenant clusters, or clusters where only cluster admins can create these policies, are much less exposed.","user_interaction":"no","needs_special_setup":"yes","severity_if_unknown":"critical"},"cost_usd":0.00076,"input_tokens":4333,"output_tokens":653,"severity_before":"critical"},"analyst_status":null,"analyst_note":null,"search":"'-122303':12A,15A '-2026':11A,14A '1.17.0':24B,62C '1.19.1':26B '1.19.2':64C 'abus':33B 'across':57B 'allow':71C 'attack':50B,86C,99C 'attacker-chosen':98C 'author':67C 'background':42B,105C 'bypass':68C 'caus':102C 'cel':90C 'chosen':100C 'cluster':59B,114C 'cluster-wid':113C 'contain':65C 'control':43B,106C 'cve':10A,13A 'deploy':54B,110C 'exist':37B,84C 'fabric':93C 'infrastructur':16B 'kubernet':17B 'kyverno':1A,18B,22B,60C 'let':27B 'liter':92C 'make':40B 'map':91C 'metadata.namespace':101C 'multi':20B 'multi-ten':19B 'mutat':36B,83C 'mutate-exist':35B,82C 'namespac':2A,9A,32B,48B,72C,79C 'namespacedmutatingpolici':34B,81C 'one':31B 'overwrit':5A,44B,52B,75C,108C 'polici':56B,112C 'privileg':104C 'resourc':6A,45B,76C 'return':88C 'rule':38B 'secret':53B,109C 'target':95C 'targetmatchconstraints.expression':85C 'tenant':3A,21B,73C 'user':29B 'version':23B 'via':80C 'vulner':69C 'wide':115C","nicknames":[],"mitigations":[],"who_affected":"Clusters running Kyverno from 1.17.0 before 1.19.2 that let namespace tenants create NamespacedMutatingPolicy resources with mutate-existing rules. Single-tenant clusters, or clusters where only cluster admins can create these policies, are much less exposed.","tier":"B","verified":{},"analyst_revisit_at":null,"fix_status":"available","audience":"businesses","plain_action":null,"pkeys":[],"ptokens":[],"labels":["critical","infrastructure","kubernetes","kyverno","multitenant"],"campaign_type":null,"first_public_at":"2026-10-21T15:40:55+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","cvss_by":"disclosure@vulncheck.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-122303","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-122303","severity":null,"published_at":"2026-11-05T03:17:22+00:00","modified_at":"2026-11-05T03:17:22+00:00","first_seen_at":"2026-11-05T03:31:40+00:00","fetched_at":"2026-11-05T03:31:40+00:00","note":null}],"documents":[{"id":72683,"url":"https://github.com/kyverno/kyverno/security/advisories/GHSA-jcw5-3wcg-fqx5","title":"Vendor advisory: github.com","kind":"vendor","source":"nvd","publisher":"vendor","text":null,"published_at":"2026-10-21T15:40:55+00:00","relation":"advisory","confidence":null,"note":"Vendor advisory: github.com"},{"id":72684,"url":"https://www.vulncheck.com/advisories/kyverno-1.17.0-before-1.19.2-cross-namespace-resource-overwrite-via-namespacedmutatingpolicy","title":"Third-party advisory: www.vulncheck.com","kind":"advisory","source":"nvd","publisher":"research","text":null,"published_at":null,"relation":"advisory","confidence":null,"note":"Third-party advisory: www.vulncheck.com"}],"exploit_sources":[],"notice":"Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}