CVE-2020-7069: PHP Information Disclosure Vulnerability

CVE-2020-7069 Overview

CVE-2020-7069 is a cryptographic vulnerability in PHP affecting the openssl_encrypt() function when using AES-CCM mode. When a 12-byte initialization vector (IV) is provided, only the first 7 bytes are actually utilized by the encryption routine. This truncation significantly weakens the cryptographic security of the encryption operation and can result in incorrect encryption data, potentially exposing sensitive information to attackers.

Critical Impact

Applications relying on AES-CCM encryption with 12-byte IVs have significantly reduced cryptographic security, potentially allowing attackers to compromise confidentiality and integrity of encrypted data.

Affected Products

• PHP versions 7.2.x below 7.2.34
• PHP versions 7.3.x below 7.3.23
• PHP versions 7.4.x below 7.4.11
• Fedora 31, 32, 33
• Debian Linux 10.0
• openSUSE Leap 15.1 and 15.2
• Canonical Ubuntu Linux 12.04, 14.04, 16.04, 18.04, 20.04
• NetApp Clustered Data ONTAP
• Oracle Communications Diameter Signaling Router
• Tenable Tenable.sc

Discovery Timeline

• October 2, 2020 - CVE-2020-7069 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2020-7069

Vulnerability Analysis

This vulnerability stems from improper handling of initialization vectors in PHP's OpenSSL wrapper when using AES-CCM (Counter with CBC-MAC) authenticated encryption mode. The AES-CCM cipher mode requires careful IV management since the nonce length directly impacts security guarantees. When developers supply a standard 12-byte IV to openssl_encrypt(), the PHP implementation incorrectly truncates this value to only 7 bytes.

The IV truncation has two severe consequences. First, it drastically reduces the effective keyspace for the nonce, making it far easier for an attacker to predict or brute-force IV values. With only 7 bytes of effective IV space instead of 12, the collision probability increases exponentially. Second, the truncation causes encryption output to differ from what the developer intended, leading to data that cannot be properly decrypted by correctly-implemented AES-CCM libraries expecting the full IV.

Root Cause

The root cause is an input validation error in PHP's OpenSSL extension specifically affecting AES-CCM mode IV handling. The implementation fails to properly validate and utilize the complete initialization vector length when processing 12-byte IVs. This represents a CWE-20 (Improper Input Validation) combined with CWE-326 (Inadequate Encryption Strength) issue, where the cryptographic parameters are not correctly applied to the underlying encryption operation.

Attack Vector

An attacker can exploit this vulnerability through network-based attacks against applications that rely on AES-CCM encryption for data protection. The attack does not require authentication or user interaction. The exploitation scenario involves:

1. Identifying a PHP application using openssl_encrypt() with AES-CCM mode and 12-byte IVs
2. Exploiting the reduced IV space to perform cryptographic attacks such as IV collision attacks
3. Potentially recovering plaintext data or forging authenticated ciphertext due to weakened MAC security

The vulnerability affects the confidentiality and integrity of encrypted communications, though it does not directly impact system availability. Applications performing inter-system encrypted communication or storing encrypted sensitive data are at particular risk.

Detection Methods for CVE-2020-7069

Indicators of Compromise

• PHP applications using openssl_encrypt() with aes-*-ccm cipher modes and 12-byte IV parameters
• Unexpected decryption failures when communicating with non-PHP systems using standard AES-CCM implementations
• Log entries indicating encryption/decryption mismatches in applications using AES-CCM mode

Detection Strategies

• Audit PHP source code for calls to openssl_encrypt() using AES-CCM cipher modes (e.g., aes-128-ccm, aes-256-ccm)
• Verify installed PHP versions against affected version ranges: 7.2.x < 7.2.34, 7.3.x < 7.3.23, 7.4.x < 7.4.11
• Use static analysis tools to identify cryptographic function calls with CCM mode specifications
• Review application logs for encryption-related errors that may indicate IV handling issues

Monitoring Recommendations

• Implement version monitoring for PHP installations across infrastructure to detect vulnerable deployments
• Monitor for applications reporting decryption errors when processing AES-CCM encrypted data
• Track security advisory feeds from PHP, distribution vendors, and affected third-party products for related updates

How to Mitigate CVE-2020-7069

Immediate Actions Required

• Upgrade PHP to version 7.2.34, 7.3.23, or 7.4.11 or later depending on your current branch
• Audit all applications using openssl_encrypt() with AES-CCM mode to identify affected code paths
• Consider temporarily switching to AES-GCM mode which does not have this IV truncation issue
• Re-encrypt any sensitive data that was encrypted using vulnerable AES-CCM implementations

Patch Information

Security patches are available from PHP and all major Linux distributions. The following resources provide patched versions:

• PHP Bug Report #79601 - Official PHP bug tracker with fix details
• Ubuntu Security Notice USN-4583-1 - Ubuntu patched packages
• Debian Security Advisory DSA-4856 - Debian patched packages
• Gentoo GLSA 202012-16 - Gentoo security update
• NetApp Security Advisory NTAP-20201016 - NetApp advisory
• Tenable Security Notice TNS-2021-14 - Tenable.sc advisory

Workarounds

• Switch from AES-CCM to AES-GCM cipher mode which is not affected by this vulnerability
• Implement application-level IV validation to ensure full IV utilization before encryption
• Use alternative cryptographic libraries such as libsodium for authenticated encryption requirements
• If AES-CCM must be used, consider using 7-byte IVs explicitly to match the actual behavior until patched

# Verify PHP version to check if vulnerable
php -v

# Check for AES-CCM usage in PHP codebase
grep -r "openssl_encrypt" /var/www/ | grep -i "ccm"

# Update PHP on Debian/Ubuntu
sudo apt update && sudo apt upgrade php

# Update PHP on RHEL/CentOS/Fedora
sudo dnf update php