Heap Overflow in yaml-cpp via Scanner Component

Executive Summary

CVE-2026-75432 is a stack underflow vulnerability in the yaml-cpp library version 0.9.0. It occurs when a malformed YAML document causes the scanner to pop or push an indentation that was never pushed onto the stack. This leads to accessing an empty stack, causing undefined behavior. In debug builds, it crashes deterministically. In release builds, it causes an out-of-bounds read, potentially leaking information or causing a denial-of-service.

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Detection Guidance

Detect this vulnerability by checking if your system uses yaml-cpp version 0.9.0. Run: yaml-cpp --version or check package manager (e.g., dpkg -l | grep yaml-cpp). Test with a malformed 96-byte YAML input to trigger the crash or DoS condition.

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Impact Analysis

This vulnerability can allow remote attackers to crash applications using yaml-cpp 0.9.0 by sending a malformed 96-byte YAML input. This results in a denial-of-service condition or potential information leakage. Systems parsing untrusted YAML files are at risk of exploitation.

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Compliance Impact

This vulnerability could potentially impact compliance with GDPR and HIPAA by enabling denial-of-service (DoS) attacks or information leakage through malformed YAML parsing. A successful exploit may cause system crashes or expose sensitive data during parsing of untrusted input, which could violate data integrity and confidentiality requirements under these regulations.

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Mitigation Strategies

Upgrade yaml-cpp to a patched version that includes the fix for the stack underflow vulnerability. Apply the patch from the pull request (PR #1476) or update to a newer release. Avoid parsing untrusted YAML files until patched.

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