Executive brief
yaml-cpp is a YAML parser library used in applications that process YAML configuration files and data. A flaw in the Scanner component allows a remote attacker to cause a denial of service by triggering a crash through malformed YAML input that exploits improper stack management.
Technical details
The vulnerability is a stack underflow (CWE-822) in the Scanner::PopIndent() and Scanner::PushIndentTo() functions in src/scanner.cpp. When parsing specially crafted YAML, the indentation stack can be popped beyond its valid bounds, causing a dereference of an empty stack and a deterministic crash. This is triggered via network input when an application uses yaml-cpp to parse untrusted YAML data.
Affected products
- yaml-cpp yaml-cpp 0.9.0
Timeline
- 2026-09-22: disclosed
- 2026-08-10: patched