How severe is CVE-2026-45321?

CVE-2026-45321 has a CVSS score of 9.6/10, rated CRITICAL. Immediate patching is strongly recommended.

Which packages are affected by CVE-2026-45321?

CVE-2026-45321 affects the following packages: @tanstack/arktype-adapter (npm), @tanstack/eslint-plugin-router (npm), @tanstack/eslint-plugin-start (npm), @tanstack/history (npm), @tanstack/nitro-v2-vite-plugin (npm), @tanstack/react-router (npm), @tanstack/react-router-devtools (npm), @tanstack/react-router-ssr-query (npm), and 76 more. Ecosystems affected: npm.

How do I fix CVE-2026-45321?

Update @tanstack/arktype-adapter to 1.166.16 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-45321 is resolved across your whole dependency graph.

How do I detect CVE-2026-45321 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @tanstack/arktype-adapter. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate CVE-2026-45321 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2026-45321?

O3 pinpoints whether CVE-2026-45321 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is CVE-2026-45321 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-45321 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-2026-45321?

CVE-2026-45321 has an EPSS (Exploit Prediction Scoring System) score of 2.3%, placing it in the 82th 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.

Is CVE-2026-45321 in the CISA Known Exploited Vulnerabilities catalog?

Yes. CVE-2026-45321 (TanStack Unspecified Vulnerability) was added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2026-05-27. CISA required all US federal civilian agencies to remediate this vulnerability by 2026-06-10. The required action was: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. This CVE has been used in known ransomware campaigns. Being listed in the KEV catalog is the strongest possible confirmation of active exploitation — treat this as a critical priority.

What type of vulnerability is CVE-2026-45321?

CVE-2026-45321 is classified as CWE-506 (CWE-506). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-45321 published, and has it been updated?

CVE-2026-45321 was published on May 12, 2026 and was last updated on July 15, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CVE-2026-45321: @tanstack/arktype-adapter (Critical 9.6)

EPSS Exploitation Probability

via FIRST.org ↗

2.3%probability of exploitation in next 30 days

Lower Risk82th percentile0.00%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Blast Radius

84 pkgs affected

Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.

@tanstack/arktype-adapternpm

813downloads / week

@tanstack/eslint-plugin-routernpm

353Kdownloads / week

@tanstack/eslint-plugin-startnpm

17Kdownloads / week

Description

On 2026-05-11, between approximately 19:20 and 19:26 UTC, 84 malicious versions across 42 @tanstack/* packages were published to the npm registry. The publishes were authenticated via the legitimate GitHub Actions OIDC trusted-publisher binding for TanStack/router, but the publish workflow itself was not modified. The attacker chained three known vulnerability classes — a pull_request_target "Pwn Request" misconfiguration, GitHub Actions cache poisoning across the fork↔base trust boundary, and runtime memory extraction of the OIDC token from the Actions runner process — to publish credential-stealing malware under a trusted identity. Each affected package received exactly two malicious versions, published a few minutes apart.

Affected Packages

84 total 84 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`@tanstack/arktype-adapter`	≥ 1.166.12&&< 1.166.16	1.166.16
📦npm	`@tanstack/eslint-plugin-router`	≥ 1.161.9&&< 1.161.13	1.161.13
📦npm	`@tanstack/eslint-plugin-start`	≥ 0.0.4&&< 0.0.8	0.0.8
📦npm	`@tanstack/history`	≥ 1.161.9&&< 1.161.13	1.161.13
📦npm	`@tanstack/nitro-v2-vite-plugin`	≥ 1.154.12&&< 1.154.16	1.154.16
📦npm	`@tanstack/react-router`	≥ 1.169.5&&< 1.169.9	1.169.9

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @tanstack/arktype-adapter. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update @tanstack/arktype-adapter to 1.166.16 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-45321 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-45321 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to CVE-2026-45321. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

On 2026-05-11, between approximately 19:20 and 19:26 UTC, 84 malicious versions across 42 @tanstack/* packages were published to the npm registry. The publishes were authenticated via the legitimate GitHub Actions OIDC trusted-publisher binding for TanStack/router, but the publish workflow itself was not modified. The attacker chained three known vulnerability classes — a pull_request_target "Pwn Request" misconfiguration, GitHub Actions cache poisoning across the fork↔base trust boundary, and runtime memory extraction of the OIDC token from the Actions runner process — to publish credential-s

O3 Security · Impact-Aware SCA

Is CVE-2026-45321 in your dependencies?

O3 detects CVE-2026-45321 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works

CVE-2026-45321