Vulnerability Snapshot
CVE-2026-125331 is rated CRITICAL — exploitation is trivial or already observed in the wild and impact is severe. Patch immediately, not on the next maintenance window.
Executive Summary
HarnessRouter is a self-hosted unified API for running agent harnesses with sessions, streaming, files, cancellation, and failure handling. Prior to 0.31.8, a console that is not in self-hosted mode attaches the server's internal key to requests carrying an Authorization header before validating the bearer, while the service-only PUT and GET /v1/orgs/{org}/connections/{name}, PUT /v1/orgs/{org}/policy/{backend}, and /internal/* routes trust that key and take the organization from the URL. In a multi-organization deployment, a remote caller can use a made-up bearer to rewrite another organization's provider connection to an attacker-controlled endpoint, causing later prompts to be disclosed and attacker-controlled responses to influence tasks. This issue is fixed in version 0.31.8.
Why It Matters
CVE-2026-125331 is rated CRITICAL severity, requiring immediate attention from security teams.
CVSS Base Score: 9.1/10
🛡️What Defenders Should Check
Use Vulnios to continuously monitor your exposure to CVE-2026-125331 and similar vulnerabilities.
References & Sources
How Vulnios Detects This
Vulnios scans for this vulnerability using Trivy and Grype for SBOM-based CVE matching and Vulnios CVE feed continuous monitoring against your asset inventory. Run a scan against your environment to see whether you are exposed; findings are linked back to the original CVE record so triage starts with the patch path already known.
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Sources
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Frequently Asked Questions
What is CVE-2026-125331?
CVE-2026-125331 is a critical-severity vulnerability tracked under the Common Vulnerabilities and Exposures program. HarnessRouter is a self-hosted unified API for running agent harnesses with sessions, streaming, files, cancellation, and failure handling. Prior to 0.31.8, a console that is not in self-hosted mode a
Am I affected?
Affected technology is listed in the Affected Products section above. If your asset inventory contains any of them, assume in-scope until you can prove otherwise.
How urgent is the response?
Critical: do not wait for your normal patch cycle. Verify exposure today, apply the vendor patch immediately, and add detection rules for any post-exploit indicators.
How do I remediate?
Apply the vendor patch listed in the upstream advisory linked under Sources. If the patch is not yet available, follow the vendor-supplied workaround (often a config flag or feature disable) and add detections for the published exploit pattern in your SIEM. Re-scan after the patch lands to confirm the finding clears.
Where can I track exploitation activity?
Watch CISA's Known Exploited Vulnerabilities catalog for CVE-2026-125331. Cross-reference with public exploit databases and your own SIEM/IDS for indicator-of-compromise patterns. Vulnios tracks KEV status automatically and surfaces it on the asset findings view.
How does Vulnios help with this?
Vulnios continuously cross-references your asset inventory against the live CVE feed (NVD, vendor advisories, CISA KEV, and curated OSINT). When a new CVE matches your environment, you get a prioritized finding with the severity, KEV status, exploit-prediction (EPSS), and a direct path to the vendor patch. You can start a free scan from the homepage.
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