CVE-2026-55636 is a medium-severity incorrect authorization vulnerability in github.com/projectcapsule/capsule (go), affecting versions >= 0.13.0, < 0.13.6. It is fixed in 0.13.6.
Summary Capsule v0.13.2 webhook rules contain namespace/finalize (singular) instead of namespaces/finalize (plural). K8s requires plural. The finalize defense from CVE-2026-30963 fix is absent. Details PUT to /api/v1/namespaces/<ns>/finalize has resource=namespaces (plural). The singular rule never matches. matchPolicy: Equivalent does not compensate. PoC Confirmed on kind + Capsule v0.13.2. alice (non-admin with namespaces/finalize RBAC): kubectl label --as=alice = DENIED (control). kubectl replace --raw /finalize --as=alice = 200 OK (bypass). Tenant label changed. Impact Namespace tenant-label hijack. Same threat model as CVE-2026-30963. One-char fix: namespace/finalize -> namespaces/finalize. The CVE-2026-30963 fix in Capsule v0.13.2 added subresource entries to the namespace validating webhook, but charts/capsule/templates/configuration.yaml line 105 contains a singular/plural typo: namespace/finalize instead of namespaces/finalize. Kubernetes webhook rules require the plural resource name. The finalize subresource defense is entirely absent. Details In Kubernetes admission webhooks, rules.resources matches against the plural resource name. A PUT to /api/v1/namespaces/<ns>/finalize has resource=namespaces (plural). The rule namespace/finalize (singular) never matches any real API request. The matchPolicy: Equivalent setting does NOT compensate (it handles API group/version variations, not resource name typos). PoC Confirmed on kind cluster + Capsule v0.13.2 (Helm chart): Impact Namespace tenant-label hijack via the finalize subresource bypass. Same threat model as CVE-2026-30963. One-character fix needed: namespace/finalize -> namespaces/finalize.
The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions. Typical impact: unauthorized data access or execution of privileged operations.
CVE-2026-55636 has a CVSS score of 5.7 (Medium). The vector is network-reachable, high privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment.
A fixed version is available (0.13.6). Upgrading removes the vulnerable code path.
go
github.com/projectcapsule/capsule (>= 0.13.0, < 0.13.6)github.com/projectcapsule/capsule → 0.13.6 (go)Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
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Upgrade github.com/projectcapsule/capsule to 0.13.6 or later to resolve this vulnerability.
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
CVE-2026-55636 is a medium-severity incorrect authorization vulnerability in github.com/projectcapsule/capsule (go), affecting versions >= 0.13.0, < 0.13.6. It is fixed in 0.13.6. The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions.
CVE-2026-55636 has a CVSS score of 5.7 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
github.com/projectcapsule/capsule (go) versions >= 0.13.0, < 0.13.6 is affected.
Yes. CVE-2026-55636 is fixed in 0.13.6. Upgrade to this version or later.
Whether CVE-2026-55636 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
Upgrade github.com/projectcapsule/capsule to 0.13.6 or later.