Summary
Fission: Cross-namespace Environment reference in Package allows build-time command execution and SA token exfiltration
Fission's buildermgr controller processed Package CRDs without verifying that Package.spec.environment.namespace matched Package.metadata.namespace.
Details
An attacker with packages.fission.io/create in their own namespace could set spec.environment.namespace to any other tenant's namespace. The controller then used its high-privilege service account to fetch the Environment
cross-namespace and dispatch the build command into the victim namespace's builder pod.
The build command's stdout is written verbatim into Package.status.buildlog. By running malicious code through an npm preinstall lifecycle hook (or any equivalent build step), the attacker could read the victim namespace'sfission-builder Bearer token from inside that builder pod and surface it through the build log, then use the leaked token to read every Secret and ConfigMap in the victim namespace.
Behavioural change
Packages that explicitly set spec.environment.namespace to a different namespace are now rejected at admission. Empty-string remains accepted (resolves to the package's own namespace, the same as the prior implicit behaviour).
Impact
Cross-tenant compromise: a package author in one namespace could execute code inside another tenant's builder pod and exfiltrate that namespace's fission-builder service-account token, giving namespace-wide secret and configmap read in
the victim namespace.
The application does not perform an authorization check before performing a sensitive operation. Typical impact: unauthorized access to restricted functionality or data.
CVE-2026-49821 has a CVSS score of 7.7 (High). The vector is network-reachable, low privileges required, and no user interaction. 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 (1.24.0); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
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.
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. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Fixed in #3379 and released in v1.24.0. Two checks in series:
- Admission webhook (
pkg/webhook/package.go::Validate) rejectsPackage.spec.environment.namespace != Package.metadata.namespace. An empty namespace is still accepted; the controllers default it to the package's own namespace. - Controller belt-and-braces: the same check is repeated in
pkg/buildermgr/pkgwatcher.go::buildandpkg/buildermgr/common.go::buildPackagebefore the cross-namespaceEnvironments(...).Getcall, so a stale Package CR or a
webhook-bypass cluster (failurePolicy=Ignore) cannot exploit the primitive either.
Frequently Asked Questions
- What is CVE-2026-49821? CVE-2026-49821 is a high-severity missing authorization vulnerability in github.com/fission/fission (go), affecting versions <= 1.23.0. It is fixed in 1.24.0. The application does not perform an authorization check before performing a sensitive operation.
- How severe is CVE-2026-49821? CVE-2026-49821 has a CVSS score of 7.7 (High). 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.
- Which versions of github.com/fission/fission are affected by CVE-2026-49821? github.com/fission/fission (go) versions <= 1.23.0 is affected.
- Is there a fix for CVE-2026-49821? Yes. CVE-2026-49821 is fixed in 1.24.0. Upgrade to this version or later.
- Is CVE-2026-49821 exploitable, and should I be worried? Whether CVE-2026-49821 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
- What actually determines whether CVE-2026-49821 is exploitable, and how bad it is? 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.
- How do I fix CVE-2026-49821? Upgrade
github.com/fission/fissionto 1.24.0 or later.