CVE-2026-15620 Overview
CVE-2026-15620 is a server-side request forgery (SSRF) vulnerability in the mosaxiv/clawlet project through version 0.2.10. The flaw resides in the tools.webFetch function within tools/tool_web_fetch.go. An authenticated remote attacker can manipulate input to the fetch function to force the server to issue arbitrary HTTP requests. A public proof-of-concept has been disclosed, and the reported GitHub issue was closed with the label "not planned," indicating no vendor fix is currently in progress. The weakness is categorized under CWE-918: Server-Side Request Forgery.
Critical Impact
Remote attackers with low privileges can coerce the clawlet server into making outbound HTTP requests to attacker-chosen destinations, enabling reconnaissance of internal networks and access to metadata services.
Affected Products
- mosaxiv clawlet versions up to and including 0.2.10
- Deployments exposing the webFetch tool endpoint
- Any downstream integrations invoking tools/tool_web_fetch.go
Discovery Timeline
- 2026-07-14 - CVE-2026-15620 published to the National Vulnerability Database (NVD)
- 2026-07-14 - Last updated in NVD database
Technical Details for CVE-2026-15620
Vulnerability Analysis
The vulnerability exists in the webFetch tool implementation of clawlet, a Go-based utility. The function accepts a URL parameter and issues an outbound HTTP request without validating the destination against a deny-list of internal address ranges. As a result, an attacker supplying a URL such as one pointing to 127.0.0.1, 169.254.169.254, or an RFC1918 range can make the clawlet server relay requests to those destinations. The public disclosure and vendor response, closing the issue as "not planned," mean administrators must apply compensating controls rather than rely on an upstream patch.
Root Cause
The root cause is missing URL validation in tools.webFetch inside tools/tool_web_fetch.go. The function trusts caller-supplied URLs and delegates directly to Go's HTTP client, which resolves and follows redirects without host allow-listing. There is no filter for loopback addresses, link-local ranges, private IP space, or cloud metadata endpoints.
Attack Vector
Exploitation requires network access to the clawlet service and low-level authenticated privileges to invoke the webFetch tool. The attacker submits a crafted URL argument to the tool. The server dereferences the URL server-side, returning response data or side-effects that leak information about internal services. Cloud-hosted deployments face additional risk because instance metadata services can expose IAM credentials to callers of the metadata endpoint.
No verified exploit code is published. Refer to the GitHub Issue Discussion and the VulDB Vulnerability Report for further technical context.
Detection Methods for CVE-2026-15620
Indicators of Compromise
- Outbound HTTP requests from the clawlet host to loopback, link-local (169.254.0.0/16), or RFC1918 addresses that do not match normal application behavior.
- Requests originating from the clawlet process targeting cloud metadata endpoints such as 169.254.169.254 or metadata.google.internal.
- Unusual invocation frequency or diverse destination hosts recorded in webFetch tool logs.
Detection Strategies
- Instrument the webFetch tool to log every requested URL, source identity, and resolved IP address for correlation.
- Deploy egress network monitoring that alerts on connections from the clawlet service to internal-only subnets or metadata IPs.
- Baseline expected external destinations for clawlet and alert on deviations.
Monitoring Recommendations
- Forward application and proxy logs to a centralized analytics platform and correlate webFetch invocations with destination IP reputation data.
- Monitor cloud provider audit logs for anomalous metadata service access originating from clawlet workloads.
- Track authentication events preceding webFetch calls to identify abuse by low-privilege accounts.
How to Mitigate CVE-2026-15620
Immediate Actions Required
- Restrict network egress from the clawlet host using host firewall or cloud security group rules that block private, loopback, and metadata address ranges.
- Place clawlet behind an authenticated forward proxy that enforces URL allow-listing for outbound HTTP requests.
- Disable or gate the webFetch tool if it is not required for operational workloads.
Patch Information
No vendor patch is available. The upstream maintainer closed the reported GitHub issue with the label "not planned." Consumers should fork the repository and add URL validation in tools/tool_web_fetch.go or apply the workarounds below. Additional records are available in the VulDB CVE Record.
Workarounds
- Implement a wrapper around webFetch that resolves the requested hostname and rejects any request whose destination IP falls in loopback, link-local, private, or metadata ranges.
- Enforce IMDSv2 on AWS deployments to require a session token for metadata access, reducing SSRF blast radius.
- Run clawlet in a network namespace or container with restricted egress routes to trusted external destinations only.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
