CVE-2026-15619 Overview
CVE-2026-15619 is a Server-Side Request Forgery (SSRF) vulnerability affecting mosaxiv clawlet versions up to 0.2.10. The flaw resides in the web_fetch function located in tools/tool_web_fetch.go, part of the IPv4 Handler component. An unauthenticated remote attacker can manipulate the url argument to coerce the application into issuing arbitrary HTTP requests on their behalf. A public exploit has been disclosed, and the associated GitHub issue was closed with the label "not planned", indicating no fix is currently intended by the maintainer. The weakness is classified under CWE-918: Server-Side Request Forgery.
Critical Impact
Attackers can abuse the vulnerable web_fetch function to reach internal services, cloud metadata endpoints, or other restricted network resources through the clawlet host.
Affected Products
- mosaxiv clawlet versions up to and including 0.2.10
- The tools/tool_web_fetch.go file (IPv4 Handler component)
- Deployments exposing the web_fetch function to untrusted input
Discovery Timeline
- 2026-07-14 - CVE-2026-15619 published to NVD
- 2026-07-15 - Last updated in NVD database
Technical Details for CVE-2026-15619
Vulnerability Analysis
The vulnerability exists in the web_fetch function within tools/tool_web_fetch.go. The function accepts a user-controlled url argument and performs a server-side HTTP request without adequate validation of the destination. Because the IPv4 Handler does not restrict target addresses, an attacker can direct requests to arbitrary hosts, including internal network ranges and loopback interfaces. This allows the attacker to pivot from an externally reachable endpoint into internal infrastructure that would otherwise be unreachable. The maintainer closed the corresponding GitHub Issue #13 with the label "not planned", so no upstream patch is expected.
Root Cause
The root cause is missing validation and filtering of the url argument before it is passed to the outbound HTTP client. The IPv4 Handler does not enforce an allowlist of permitted hosts, block private address ranges (RFC 1918), reject link-local addresses, or prevent DNS rebinding. Any URL supplied by the caller is fetched as-is by the server.
Attack Vector
Exploitation occurs remotely over the network. An attacker submits a crafted url parameter pointing to an internal resource such as http://169.254.169.254/, http://127.0.0.1:8080/, or an internal service endpoint. The clawlet server issues the request from its own network position and returns the response, disclosing internal data or triggering unintended side effects. User interaction (following a link or triggering the request) is required per the CVSS metrics, but no authentication is needed. A public exploit is referenced in the VulDB entry for CVE-2026-15619.
See the mosaxiv clawlet GitHub repository for source-level analysis of the vulnerable handler.
Detection Methods for CVE-2026-15619
Indicators of Compromise
- Outbound HTTP requests from the clawlet process targeting RFC 1918 addresses (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) or loopback 127.0.0.0/8.
- Requests originating from clawlet toward cloud metadata endpoints such as 169.254.169.254 or metadata.google.internal.
- Unusual spikes in inbound requests to the web_fetch endpoint containing non-standard schemes or encoded IP literals.
Detection Strategies
- Inspect application logs for web_fetch invocations and correlate the supplied url argument against an allowlist of expected external destinations.
- Deploy egress filtering at the network layer and alert when the clawlet host initiates connections to internal subnets or metadata services.
- Monitor DNS resolution activity from the clawlet host for domains that resolve to private IP ranges, which can indicate DNS rebinding attempts.
Monitoring Recommendations
- Enable verbose HTTP client logging in clawlet to capture full target URLs, response codes, and response sizes for every web_fetch call.
- Forward host and network telemetry to a centralized analytics platform for correlation across the clawlet fleet.
- Establish baselines for normal web_fetch traffic and alert on deviations such as new destination hosts, non-HTTP schemes, or requests to IP literals.
How to Mitigate CVE-2026-15619
Immediate Actions Required
- Restrict network access to the clawlet service so only trusted clients can invoke the web_fetch endpoint.
- Place clawlet behind an egress proxy that enforces an allowlist of permitted outbound destinations and blocks private, loopback, and link-local ranges.
- Remove or disable the web_fetch tool if it is not required for your deployment.
Patch Information
No vendor patch is available. The upstream GitHub Issue #13 was closed with the label "not planned", meaning the maintainer does not intend to release a fix. Operators must apply compensating controls or fork the project to introduce URL validation in tools/tool_web_fetch.go.
Workarounds
- Introduce a wrapper around web_fetch that validates the resolved IP address of the target host and rejects private, loopback, multicast, and link-local ranges.
- Block cloud metadata endpoints (169.254.169.254, fd00:ec2::254) at the host firewall for any system running clawlet.
- Require authentication and rate limiting on any interface that exposes web_fetch to reduce opportunistic abuse.
# Example iptables rules to block SSRF-relevant destinations from the clawlet host
iptables -A OUTPUT -m owner --uid-owner clawlet -d 169.254.169.254 -j REJECT
iptables -A OUTPUT -m owner --uid-owner clawlet -d 127.0.0.0/8 -j REJECT
iptables -A OUTPUT -m owner --uid-owner clawlet -d 10.0.0.0/8 -j REJECT
iptables -A OUTPUT -m owner --uid-owner clawlet -d 172.16.0.0/12 -j REJECT
iptables -A OUTPUT -m owner --uid-owner clawlet -d 192.168.0.0/16 -j REJECT
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
