CVE-2017-1000158

What it actually does

Integer overflow in PyString_DecodeEscape causes heap-based buffer overflow enabling potential arbitrary code execution in vulnerable CPython interpreters.

Why it matters to the business

Unpatched Python environments risk remote code execution that can lead to data theft, service disruption, or full system takeover across applications and dependent services.

How an attack unfolds

An attacker supplies a maliciously crafted string to any code path invoking PyString_DecodeEscape; the integer overflow miscalculates buffer size, resulting in a heap overflow that an attacker can leverage to overwrite memory structures and execute arbitrary code.

How to fix it

Upgrade python/cpython to commit ca079a3ea30098aff3197c559a0e32d42dda6d84 or later; upgrade policy-controller-fips and policy-controller-tester-fips to 0.8.4-r2 or later. Remove or isolate any remaining instances of Python 2.7.13 or earlier.

How to confirm the fix worked

Confirm installed Python versions exceed 2.7.13, run regression tests with known overflow-triggering inputs against PyString_DecodeEscape, and verify no vulnerable binaries remain in runtime paths.

Typical attack path

1. Locate an exposed Python application or service that processes attacker-controlled input through string decoding routines
2. Transmit a specially formed string designed to trigger the overflow in PyString_DecodeEscape
3. Manipulate heap layout to achieve code execution and establish persistence or exfiltrate data

How to detect it

Search process execution logs and application telemetry for crashes or segmentation faults occurring during string decode operations; correlate with any services still running Python versions prior to the listed fixes.

What your security team should do

• Immediately inventory all Python 2.7.x deployments and schedule upgrades to fixed versions
• Block or sandbox services that still rely on unpatched Python interpreters until remediation completes
• Add version checks for Python runtimes to continuous compliance scanning