How severe is CVE-2026-77426?

No CVSS score has been assigned to CVE-2026-77426 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-77426?

CVE-2026-77426 affects the following packages: unleash-server (npm). Ecosystems affected: npm.

How do I fix CVE-2026-77426?

Update unleash-server to 8.0.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-77426 is resolved across your whole dependency graph.

How do I detect CVE-2026-77426 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for unleash-server, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-77426 if there is no patch (or I can't update yet)?

Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Is CVE-2026-77426 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-77426 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-77426?

CVE-2026-77426 has an EPSS (Exploit Prediction Scoring System) score of 0.5%, placing it in the 40th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-77426?

CVE-2026-77426 is classified as CWE-639 (CWE-639), CWE-862 (CWE-862). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-77426 published, and has it been updated?

CVE-2026-77426 was published on September 22, 2026 and was last updated on September 25, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦 npm

Not in CISA KEV

CVE-2026-77426 — unleash-server

Fix: Unleash/unleash@7bb2829

CVE-2026-77426 is a CWE-639 vulnerability in unleash-server. A fix is available for unleash-server — see the affected versions and patch details below.

Unleash: Missing await on permission check + cross-project IDOR in admin API

Also known asGHSA-72h8-wp98-7hch

Published

Sep 22, 2026

Updated

Sep 25, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 16, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-77426.

EPSS Exploitation Probability

via FIRST.org ↗

0.5%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs40th percentile — riskier than 40% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

2other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

unleash-servernpm

14Kdownloads / week

Description

Summary

Multiple authorization vulnerabilities in Unleash admin API, including a critical missing await that completely bypasses a permission check.

Vulnerability 1: Missing `await` on Permission Check (HIGH)

File: src/lib/features/segment/segment-controller.ts (line 345)

POST /api/admin/segments/strategies has permission: NONE at the route level. The handler performs its own check via this.accessService.hasPermission(), but omits the await keyword. Since hasPermission() is async (returns Promise<boolean>), the variable always receives a truthy Promise object. The if (!hasFeatureStrategyPermission) check never triggers.

// BUG: missing await - hasPermission() returns Promise<boolean>
const hasFeatureStrategyPermission = this.accessService.hasPermission(
    req.user, UPDATE_FEATURE_STRATEGY, projectId, environmentId,
);
if (!hasFeatureStrategyPermission) { // Always false - Promise is truthy!
    res.status(403).send();
    return;
}

Impact: Any authenticated user can modify segment assignments on ANY strategy across ALL projects.

Fix: Add await: const hasFeatureStrategyPermission = await this.accessService.hasPermission(...)

Vulnerability 2: Cross-Project Variant Read (MEDIUM)

File: src/lib/routes/admin-api/project/variants.ts (line 213-223)

GET /api/admin/projects/:projectId/features/:featureName/environments/:environment/variants completely ignores projectId. getVariantsOnEnv() only uses featureName and environment.

Impact: Any authenticated user can read variant configs (names, weights, payloads) from any project.

Vulnerability 3: Cross-Project Strategy Read (MEDIUM)

File: src/lib/features/feature-toggle/feature-toggle-controller.ts (line 1107-1116)

GET .../strategies/:strategyId ignores all params except strategyId. Any authenticated user can read any strategy's full configuration.

Vulnerability 4: Cross-Project Environment Info Leak (MEDIUM)

File: src/lib/features/feature-toggle/feature-toggle-service.ts (line 1611)

getEnvironmentInfo() doesn't validate feature belongs to project. Compare with getFeature() which calls validateFeatureBelongsToProject().

Vulnerability 5: Cross-Project Tag Modification (LOW)

File: src/lib/features/feature-toggle/feature-toggle-controller.ts (line 576-596)

PUT /:projectId/tags accepts features array in body without validating they belong to projectId.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`unleash-server`	all versions	8.0.3`npm install unleash-server@8.0.3`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for unleash-server, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update unleash-server to 8.0.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-77426 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Frequently Asked Questions

## Summary Multiple authorization vulnerabilities in Unleash admin API, including a critical missing `await` that completely bypasses a permission check. ## Vulnerability 1: Missing `await` on Permission Check (HIGH) **File:** `src/lib/features/segment/segment-controller.ts` (line 345) `POST /api/admin/segments/strategies` has `permission: NONE` at the route level. The handler performs its own check via `this.accessService.hasPermission()`, but **omits the `await` keyword**. Since `hasPermission()` is async (returns `Promise<boolean>`), the variable always receives a truthy Promise object.