How severe is CVE-2026-53840?

No CVSS score has been assigned to CVE-2026-53840 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-53840?

CVE-2026-53840 affects the following packages: openclaw (npm). Ecosystems affected: npm.

How do I fix CVE-2026-53840?

Update openclaw to 2026.5.12 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-53840 is resolved across your whole dependency graph.

How do I detect CVE-2026-53840 in my npm dependencies?

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

How do I mitigate CVE-2026-53840 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.

Is CVE-2026-53840 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-53840 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-2026-53840?

CVE-2026-53840 has an EPSS (Exploit Prediction Scoring System) score of 0.3%, placing it in the 21th 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-2026-53840?

CVE-2026-53840 is classified as CWE-522 (CWE-522). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-53840 published, and has it been updated?

CVE-2026-53840 was published on June 16, 2026 and was last updated on August 17, 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-2026-53840 — openclaw

CVE-2026-53840 is a CWE-522 vulnerability in openclaw. A fix is available for openclaw — see the affected versions and patch details below.

OpenClaw < 2026.5.12 - Custom Header Leakage via MCP Streamable HTTP Cross-Origin Redirects

Also known asGHSA-rjxq-qqhf-8hwh

Published

Jun 16, 2026

Updated

Aug 17, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Sep 27, 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-2026-53840.

EPSS Exploitation Probability

via FIRST.org ↗

0.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs21th percentile — riskier than 21% 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.

133other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

openclawnpm

3.2Mdownloads / week

Description

Summary

OpenClaw supports remote MCP Streamable HTTP servers with operator-configured custom headers. In affected releases, those headers could be forwarded when the MCP endpoint responded with a cross-origin redirect.

This issue is limited to configured MCP Streamable HTTP servers that use custom headers. It does not expose unrelated OpenClaw credentials.

Affected configurations

This affects deployments where an MCP server is configured with:

transportType: "streamable-http"
sensitive custom headers under mcp.servers.*.headers
an MCP endpoint that is malicious, compromised, or able to redirect to another origin

Impact

Custom MCP headers, such as API keys or tenant-routing headers, could be sent to the redirect target. The exposed credential scope depends on the header the operator configured for that MCP server.

Patched Versions

The first stable patched version is 2026.5.12.

Mitigations

Upgrade to [email protected] or later. Before upgrading, avoid custom MCP headers with servers you do not fully trust, and rotate any MCP-specific credentials that may have been exposed by a redirecting endpoint.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`openclaw`	all versions	2026.5.12`npm install openclaw@2026.5.12`

Affected Products

1 product · 9 configurations

Application

openclawopenclaw

< 2026.5.12

1 version

2026.5.12

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for openclaw, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update openclaw to 2026.5.12 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-53840 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.

Frequently Asked Questions

### Summary OpenClaw supports remote MCP Streamable HTTP servers with operator-configured custom headers. In affected releases, those headers could be forwarded when the MCP endpoint responded with a cross-origin redirect. This issue is limited to configured MCP Streamable HTTP servers that use custom headers. It does not expose unrelated OpenClaw credentials. ### Affected configurations This affects deployments where an MCP server is configured with: - `transportType: "streamable-http"` - sensitive custom headers under `mcp.servers.*.headers` - an MCP endpoint that is malicious, compromi

O3 Security · Impact-Aware SCA

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