Wails: wildcardPatternToRegex allows Origin bypass via suffix match in BindingsAllowedOrigins

Security Vulnerability Report: Wails v2 — Origin Validator Bypass via Wildcard Pattern

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Summary

Wails v2 provides BindingsAllowedOrigins to restrict which web origins can invoke Go backend methods via IPC. The wildcard pattern matching in wildcardPatternToRegex converts * to .* without anchoring subcomponents, allowing suffix-matched origins to bypass the restriction.

An attacker who controls a domain sharing a prefix with the allowed origin (e.g., myapp.community when myapp.com* is configured) can invoke arbitrary bound Go methods, potentially achieving file system access, data exfiltration, or code execution depending on the application's exposed API surface.

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Vulnerability Details

Root Cause

wildcardPatternToRegex converts a wildcard pattern to a regular expression by escaping special characters and replacing * with .*. The substituted .* has no restriction — it matches any character sequence including dots and additional domain components.

Vulnerable Code

File: v2/internal/frontend/originvalidator/originValidator.go

func (v *OriginValidator) wildcardPatternToRegex(wildcardPattern string) string {
    specialChars := []string{"\\", ".", "+", "?", "^", "$", "{", "}", "(", ")", "|", "[", "]"}

    escaped := wildcardPattern
    for _, specialChar := range specialChars {
        escaped = strings.ReplaceAll(escaped, specialChar, "\\"+specialChar)
    }

    // * becomes .* — matches ANY character sequence, including dots and domain separators
    escaped = strings.ReplaceAll(escaped, "*", ".*")

    return "^" + escaped + "$"
}

The generated regex for https://myapp.com* is:

^https://myapp\.com.*$

This matches any string beginning with https://myapp.com, including:

• https://myapp.community — different TLD
• https://myapp.com.attacker.com — attacker-controlled subdomain
• https://myapp.comXXXXX — any arbitrary suffix

Scope Note

The official comment in options.go gives https://*.myapp.com as the example pattern (subdomain prefix wildcard). This pattern is not affected. The vulnerability only manifests when developers use a trailing wildcard (myapp.com*), which is a natural misuse when intending to permit a domain and all its subpaths or ports.

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Impact

Any Go method registered with Wails bindings becomes callable from the attacker's origin. Depending on the application:

• File system read / write (common in desktop apps)
• Database queries
• OS command execution (if exposed via bindings)
• Sensitive configuration or credential access

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Fix

PR: https://github.com/wailsapp/wails/pull/5074

Wildcards are now only expanded when they represent a full domain component (immediately after ://, ., or :). A wildcard appended to a partial label (e.g. com*) is stripped, preventing suffix-based bypasses. Comprehensive test suite added.

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Disclosure Timeline