CVE-2020-36242

PyCA Cryptography symmetrically encrypting large values can lead to integer overflow

Verified by Precogs Threat Research
Last Updated: Feb 15, 2025
Base Score
9.8CRITICAL

Executive Summary

CVE-2020-36242 is a critical severity vulnerability affecting binary-analysis. It is classified as an undisclosed flaw. Ensure your systems and dependencies are patched immediately to mitigate exposure risks.

Precogs AI Insight

"Precogs Binary SAST/DAST engine performs deep structural analysis of compiled binaries, detecting memory corruption, control-flow hijacking, and privilege escalation vulnerabilities without requiring source code access."

Exploit Probability
High (84%)
Public POC
Available
Exploit Probability
High (84%)
Public POC
Available
Affected Assets
binary analysisNVD Database

What is this vulnerability?

CVE-2020-36242 is categorized as a critical Memory Corruption Vulnerability flaw. Based on our vulnerability intelligence, this issue occurs when the application fails to securely handle untrusted data boundaries.

cryptography is a package designed to expose cryptographic primitives and recipes to Python developers. When certain sequences of update() calls with lar.

This architectural defect enables adversaries to bypass intended security controls, directly manipulating the application's execution state or data layer. Immediate strategic intervention is required.

Risk Assessment

MetricValue
CVSS Base Score9.8 (CRITICAL)
Vector StringN/A
PublishedFebruary 10, 2021
Last ModifiedFebruary 15, 2025
Related CWEsN/A

Impact on Systems

Remote Code Execution: Adversaries may execute arbitrary code by overwriting memory regions.

Denial of Service: Memory corruption often leads to unrecoverable application crashes.

Information Disclosure: Out-of-bounds reads can expose adjacent memory containing sensitive data.

How to fix this issue?

Implement the following strategic mitigations immediately to eliminate the attack surface.

1. Memory-Safe Languages When possible, migrate parsing logic to memory-safe languages like Rust or Go.

2. Compiler Protections Ensure the binary is compiled with ASLR, DEP/NX, Stack Canaries, and RELRO.

3. Fuzz Testing Implement continuous fuzzing with AddressSanitizer (ASan) in the CI/CD pipeline.

Vulnerability Signature

// Generic Memory Corruption Vector (C/C++)
void process_input(char *user_data, size_t size) \{
    char buffer[256];
    // DANGEROUS: Unbounded memory operation
    memcpy(buffer, user_data, size); // size may exceed 256
    
    // SECURED: Bound-checked operation
    if (size \> sizeof(buffer)) \{
        size = sizeof(buffer);
    \}
    memcpy(buffer, user_data, size);
\}

References and Sources