CVE-2022-2097: OpenSSL AES Information Disclosure Flaw

CVE-2022-2097 Overview

CVE-2022-2097 is a cryptographic vulnerability in OpenSSL affecting the AES OCB (Offset Codebook) mode encryption on 32-bit x86 platforms that utilize the AES-NI assembly optimized implementation. Under specific circumstances, the implementation fails to encrypt the entirety of the data, potentially exposing sixteen bytes of preexisting memory content or plaintext data.

This vulnerability specifically impacts scenarios where the AES-NI hardware acceleration is used on 32-bit x86 architectures. When "in place" encryption is performed, the flaw could directly reveal sixteen bytes of plaintext data. While the impact is limited to confidentiality, the exposure of unencrypted data in cryptographic operations represents a significant security concern for applications relying on AES OCB mode encryption.

Importantly, OpenSSL does not support OCB-based cipher suites for TLS and DTLS protocols, meaning standard TLS/DTLS communications are unaffected by this vulnerability.

Critical Impact

Partial encryption failure in AES OCB mode can expose up to sixteen bytes of sensitive plaintext or memory contents on affected 32-bit x86 systems using AES-NI optimization.

Affected Products

• OpenSSL 3.0.0 through 3.0.4
• OpenSSL 1.1.1 through 1.1.1p
• Fedora 35 and 36
• NetApp Active IQ Unified Manager
• NetApp Clustered Data ONTAP Antivirus Connector
• NetApp H-Series firmware (H300s, H500s, H700s, H410s, H410c)
• Siemens SINEC INS (versions up to and including 1.0 SP2)
• Debian Linux 10.0 and 11.0

Discovery Timeline

• July 5, 2022 - CVE-2022-2097 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2022-2097

Vulnerability Analysis

This vulnerability stems from a flaw in the AES-NI assembly optimized implementation of AES OCB mode encryption specifically for 32-bit x86 platforms. The encryption routine fails to properly process all data blocks under certain conditions, leaving a 16-byte (128-bit) block unencrypted.

The impact manifests in two ways depending on the encryption operation mode:

1. Standard encryption: Sixteen bytes of preexisting memory content that wasn't written to the output buffer may be revealed to an attacker
2. In-place encryption: Sixteen bytes of the original plaintext data remains unencrypted and exposed

The vulnerability is categorized under CWE-327 (Use of a Broken or Risky Cryptographic Algorithm), as the flawed implementation effectively breaks the confidentiality guarantees of the encryption operation. While AES OCB mode itself is a sound authenticated encryption algorithm, this implementation bug compromises its security properties on affected platforms.

Root Cause

The root cause lies in the AES-NI assembly optimized code path for 32-bit x86 architectures. The assembly implementation contains a logic error that causes it to skip encryption of a 16-byte data block under specific alignment or data length conditions. This results in either memory disclosure (when the output buffer contains residual data) or plaintext exposure (during in-place encryption operations).

The issue is specific to the assembly-optimized code path and does not affect the portable C implementation or 64-bit platforms.

Attack Vector

The attack vector for this vulnerability is network-based, as encrypted data transmitted over a network could contain the unencrypted 16-byte block. An attacker with the ability to capture encrypted traffic could potentially extract:

• Sensitive data from memory that was not intended to be disclosed
• Plaintext content that should have been encrypted

Exploitation requires that the target system meets all of the following conditions:

• Running on a 32-bit x86 platform
• Using OpenSSL's AES-NI assembly optimized implementation
• Employing AES OCB mode for encryption
• Processing data in a manner that triggers the specific code path with the bug

Applications using AES OCB mode for data-at-rest encryption or custom protocols (not TLS/DTLS) are most at risk.

Detection Methods for CVE-2022-2097

Indicators of Compromise

• Presence of vulnerable OpenSSL versions (1.1.1 through 1.1.1p or 3.0.0 through 3.0.4) on 32-bit x86 systems
• Applications explicitly configured to use AES OCB mode cipher operations
• Log entries or error conditions related to encryption operations producing unexpected output sizes
• Network traffic analysis showing potential plaintext leakage in encrypted streams using custom protocols

Detection Strategies

• Inventory all systems running 32-bit x86 architectures and audit their OpenSSL versions using openssl version command
• Review application code and configurations for use of AES OCB mode encryption (EVP_aes_*_ocb cipher functions)
• Implement software composition analysis (SCA) tools to identify vulnerable OpenSSL library dependencies across the environment
• Deploy network monitoring to detect anomalous patterns in encrypted traffic from affected systems

Monitoring Recommendations

• Enable detailed logging for cryptographic operations in applications using OpenSSL on 32-bit platforms
• Monitor for security advisories from vendors whose products embed OpenSSL (NetApp, Siemens, Fedora, Debian)
• Implement file integrity monitoring on OpenSSL library files to detect unauthorized modifications or failed updates
• Track EPSS score trends (currently 0.407%, 60.58th percentile) for changes in exploitation likelihood

How to Mitigate CVE-2022-2097

Immediate Actions Required

• Upgrade OpenSSL to version 3.0.5 or later for 3.0.x branch, or version 1.1.1q or later for 1.1.1 branch
• If immediate patching is not possible, avoid using AES OCB mode on affected 32-bit x86 systems
• Audit applications to identify any custom use of AES OCB mode encryption that may be affected
• Review and apply vendor-specific patches from NetApp, Siemens, Fedora, and Debian as applicable

Patch Information

OpenSSL has released patches addressing this vulnerability:

• OpenSSL 3.0.5: Fixes the issue for the 3.0.x branch (affected versions: 3.0.0-3.0.4)
• OpenSSL 1.1.1q: Fixes the issue for the 1.1.1 branch (affected versions: 1.1.1-1.1.1p)

The fixes are available in the following commits:

• OpenSSL Commit 91992567 for OpenSSL 3.0.x
• OpenSSL Commit A98F339D for OpenSSL 1.1.1

Additional vendor advisories:

• OpenSSL Security Advisory July 2022
• NetApp Security Advisory NTAP-20220715-0011
• Siemens Security Advisory SSA-332410
• Debian DSA-5343 Security Update

Workarounds

• Switch from AES OCB mode to alternative authenticated encryption modes such as AES-GCM which are not affected by this vulnerability
• Disable AES-NI hardware acceleration on affected 32-bit systems to force use of the portable C implementation (note: significant performance impact)
• Migrate affected 32-bit x86 workloads to 64-bit platforms where the vulnerability does not manifest
• Implement application-level validation to verify encryption output integrity before transmission

# Check current OpenSSL version
openssl version

# Verify platform architecture
uname -m

# Update OpenSSL on Debian/Ubuntu
sudo apt-get update && sudo apt-get install --only-upgrade openssl libssl1.1

# Update OpenSSL on RHEL/CentOS/Fedora
sudo dnf update openssl

# Verify updated version
openssl version -a