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Pinniped Supervisor Insufficient Session Expiration vulnerability

Moderate severity GitHub Reviewed Published Aug 26, 2022 in vmware-tanzu/pinniped • Updated Jan 29, 2023

Package

gomod go.pinniped.dev (Go)

Affected versions

>= 0.3.0, < 0.19.0

Patched versions

0.19.0

Description

Impact

A user authenticating to Kubernetes clusters via the Pinniped Supervisor could potentially use their access token to continue their session beyond what proper use of their refresh token might allow.

Access tokens issued by the Pinniped Supervisor have an intended expiration lifetime of approximately two minutes. The Pinniped CLI will automatically use the refresh token, which has a lifetime of approximately nine hours, to request a new access token after the access token's advertised expiration time elapses. Starting in Pinniped version 0.13.0, the Supervisor performs checks during each refresh request against the configured external identity provider to determine if the user should be allowed to continue their session. Thus, the short lifetime of the access token is intended to force users to be subjected to those checks often. For example, if a user's account in the external identity provider became locked, the next refresh would fail, and the user should lose access to the Kubernetes clusters fairly quickly. As another example, if a user's group membership changed in the external identity provider, the new group memberships would be reflected in their sessions with Kubernetes clusters within a fairly short window of time.

Access tokens are cached in a local file by the Pinniped CLI (the kubectl plugin) and are sent back to the Supervisor (via HTTPS) to receive cluster-scoped credentials. Due to a bug in this token exchange, the expiration time of the submitted access token was not checked correctly, causing expired access tokens to continue to be accepted by this endpoint until the user's backend session data is deleted, approximately nine hours after their session started. This bug could allow a legitimate user to avoid the checks performed during refresh by maliciously skipping the refresh step.

Note that the Pinniped CLI performs the refresh operation often, so the refresh checks are still performed often under normal usage of the CLI, despite this bug.

Practical impact to versions before v0.13.0 is minimal, since those versions did not perform checks against the external identity provider during refreshes. In these versions, the user can perform refreshes to get a new access tokens without restriction for approximately nine hours, so the duration of their access is effectively unchanged by this bug.

Patches

The impacted token exchange feature was first introduced in v0.3.0. Versions v0.3.0 to v0.18.0 are effected by this bug.

This vulnerability was found by the maintainers of Pinniped and fixed immediately. The fix was introduced in release v0.19.0.

Workarounds

There are no known workarounds. Upgrading the Supervisor is recommended, especially for users of v0.13.0 or newer.

References

The issue was fixed by PR #1264.

For more information

If you have any questions or comments about this advisory, please reach out to the maintainers using one of the methods described in this repo's README.md.

References

@cfryanr cfryanr published to vmware-tanzu/pinniped Aug 26, 2022
Published by the National Vulnerability Database Aug 29, 2022
Published to the GitHub Advisory Database Sep 1, 2022
Reviewed Sep 1, 2022
Last updated Jan 29, 2023

Severity

Moderate

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 v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
Low
User interaction
None
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:L/A:N

EPSS score

0.054%
(24th percentile)

Weaknesses

CVE ID

CVE-2022-31677

GHSA ID

GHSA-rp4v-hhm6-rcv9

Source code

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