SECURITY_FIX.md

Security Fix: Integer Overflow Protection in Cache Serialization

Summary

Fixed High severity integer overflow vulnerability identified by GitHub Advanced Security in PR #117.

Vulnerability

Locations: universal_cache.go lines 789 and 811

• result := make([]byte, len(bytes)+1) - Raw bytes path
• result := make([]byte, len(jsonData)+1) - JSON encoding path

Risk: Potential integer overflow when allocating memory for very large cache entries.

Fix Applied

1. Added size limit constant:

   maxCacheEntrySize = 64 * 1024 * 1024 // 64 MiB

2. Size validation before allocation:

   • Validates entry size doesn't exceed limit
   • Validates adding marker byte won't overflow
   • Returns descriptive error messages

3. Comprehensive test coverage:

   • Oversized byte slices (>64 MiB)
   • Exact max size edge case
   • Safe sizes (normal operation)
   • Large JSON data structures

Verification

✅ All tests pass with race detection ✅ No security issues (golangci-lint, gosec) ✅ 76.3% test coverage maintained

Impact

• No breaking changes
• Negligible performance overhead
• Prevents potential buffer overflows
• Predictable memory usage

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Date: January 8, 2026 Severity: High → Resolved