AI security incident: Caddy: Unicode case-folding length expansion causes incorrect split_path index in Fas...
Summary Caddy's FastCGI path splitting logic computes the split index on a lowercased copy of the request path and then uses that byte index to slice the original path. This is unsafe for Unicode because strings.ToLower() can change UTF-8 byte length for some characters. As a result, Caddy can derive an incorrect SCRIPT_NAME / SCRIPT_FILENAME and PATH_INFO , potentially causing a request that contains .php to execute a different on-disk file than intended (path confusion). In setups where an attacker can control file contents (e.g., upload features), this can lead to unintended PHP execution of non-.php files (potential RCE depending on deployment). ### Details The issue is in github.com/caddyserver/caddy/modules/caddyhttp/fastcgi.Trasnport.
Why This Is AI-Related
This page is treated as AI-specific because the source material references copilot, which places the issue inside an AI workflow, model, assistant, or supporting dependency rather than a generic software bulletin.
- copilot
Affected Workflow
Review AI plugins, copilots, model-serving helpers, CLI tools, and automation runtimes that execute system commands.
Likely Attack Path
An attacker can turn the vulnerable AI-adjacent component into a path for command execution on the host or service runtime.
Impact
The issue can create a path to command execution inside an AI-facing product, plugin, copilot, or supporting service runtime. Severity HIGH. Classification confidence 53%. Source channel GHSA.
Detection And Triage Signals
- New shell or process activity from AI-facing services
- Unexpected outbound connections or file writes after prompt or API activity
- Privilege changes, container escapes, or suspicious job execution logs
Recommended Response
- Identify every environment that runs the affected AI plugin, assistant, CLI, or supporting package.
- Patch or isolate the vulnerable component and remove risky execution permissions while validation is in progress.
- Review process execution, outbound connections, and file-write logs for signs of post-exploitation activity.
Compliance And Business Impact
Code execution paths create immediate risk of host compromise, credential theft, and downstream lateral movement.
Sources
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