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Fission runtime pods automount the fission-fetcher service-account token into the user function container, granting function code namespace-wide secret / configmap read

High severity GitHub Reviewed Published May 15, 2026 in fission/fission • Updated Jun 10, 2026

Package

gomod github.com/fission/fission (Go)

Affected versions

<= 1.22.0

Patched versions

1.23.0

Description

Summary

Fission runtime pods were created with ServiceAccountName: fission-fetcher, and the fission-fetcher ServiceAccount was granted namespace-wide get on secrets and configmaps (it needs that to load function code, env vars, and config). The runtime pod's automounted token was reachable from inside the user's function container at /var/run/secrets/kubernetes.io/serviceaccount/token, so user-supplied function code inherited the same Kubernetes API privileges and could read any secret or configmap in the function's namespace — far beyond the Function.spec.secrets allowlist that the function specification suggests.

Affected component

  • pkg/executor/executortype/poolmgr/gp_deployment.go:154-156 — pool-manager runtime pod ServiceAccountName.
  • pkg/executor/executortype/newdeploy/newdeploy.go:225-227 — new-deploy runtime pod ServiceAccountName.
  • pkg/utils/serviceaccount.go:51-64 — fission-fetcher RBAC: namespace-wide get on secrets / configmaps.

Impact

A user able to deploy or update a function in any namespace where Fission runtime pods are scheduled could:

  1. Read every secret in that namespace (TLS keys, OIDC client secrets, database credentials, cloud provider credentials).
  2. Read every configmap in that namespace.
  3. Use those credentials to pivot to other Kubernetes resources or external systems the secrets unlock.

This violates the principle that Function.spec.secrets is the authoritative declaration of which secrets a function can read.

Root cause

The fetcher sidecar legitimately needs the SA token to call the Fission control plane and fetch package archives. Setting ServiceAccountName: fission-fetcher on the pod gives every container in the pod (including the user container) the automounted token. Kubernetes does not provide per-container service-account scoping inside a single pod, so the user container has to be moved into a separate identity / token-mount scheme.

Fix

Released in v1.23.0:

  • PR #3366 (commit fe1842ef):
    • The user function container now sets AutomountServiceAccountToken: false at the container level (via projected-volume token suppression), so the user container no longer sees the pod's SA token even though the fetcher sidecar still does.
    • The fetcher sidecar retains its existing token mount (separate projected volume) since it needs cluster API access for its own work.
    • For the few legitimate use cases where a function needs its own Kubernetes API access, the user is expected to mount a different ServiceAccount via Function.spec.podspec with the minimum necessary RBAC (documented separately).

Mitigation (until upgrade)

  1. Restrict who can create / update Function and Package CRDs in your cluster — treat the ability to ship function code as equivalent to namespace-wide secret read.
  2. Reduce the fission-fetcher ClusterRole / Role scope where possible (e.g. constrain it to specific named secrets via separate Role bindings).
  3. Add NetworkPolicy egress rules denying function pods access to the Kubernetes API server (this blunts the token even if it leaks).

References

@sanketsudake sanketsudake published to fission/fission May 15, 2026
Published to the GitHub Advisory Database May 21, 2026
Reviewed May 21, 2026
Published by the National Vulnerability Database Jun 10, 2026
Last updated Jun 10, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements None
Privileges Required None
User interaction None
Vulnerable System Impact Metrics
Confidentiality High
Integrity None
Availability None
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(27th percentile)

Weaknesses

Execution with Unnecessary Privileges

The product performs an operation at a privilege level that is higher than the minimum level required, which creates new weaknesses or amplifies the consequences of other weaknesses. Learn more on MITRE.

Improper Privilege Management

The product does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control for that actor. Learn more on MITRE.

Insertion of Sensitive Information into Externally-Accessible File or Directory

The product places sensitive information into files or directories that are accessible to actors who are allowed to have access to the files, but not to the sensitive information. Learn more on MITRE.

CVE ID

CVE-2026-46617

GHSA ID

GHSA-85g2-pmrx-r49q

Source code

Credits

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