CVE-2023-0215: OpenSSL Use-After-Free Vulnerability

CVE-2023-0215 Overview

CVE-2023-0215 is a use-after-free vulnerability in the OpenSSL cryptographic library affecting the BIO_new_NDEF public API function. This helper function is used for streaming ASN.1 data via a BIO and is primarily utilized internally by OpenSSL to support SMIME, CMS, and PKCS7 streaming capabilities. The vulnerability occurs when the function fails to properly clean up the BIO chain under certain error conditions, leaving dangling pointers that can lead to a use-after-free condition when the caller subsequently calls BIO_pop().

Critical Impact

This use-after-free vulnerability can cause application crashes and denial of service conditions in systems relying on OpenSSL for cryptographic operations, affecting critical infrastructure components that use SMIME, CMS, or PKCS7 functionality.

Affected Products

• OpenSSL (multiple versions)
• Stormshield Management Center
• Various third-party products incorporating vulnerable OpenSSL versions

Discovery Timeline

• 2023-02-07 - OpenSSL releases security advisory
• 2023-02-08 - CVE-2023-0215 published to NVD
• 2025-11-04 - Last updated in NVD database

Technical Details for CVE-2023-0215

Vulnerability Analysis

The vulnerability exists in the BIO_new_NDEF function which receives a BIO from the caller and prepends a new BIO_f_asn1 filter BIO onto the front of it to form a BIO chain. When the function encounters certain error conditions—such as an invalid CMS recipient public key—the newly created filter BIO is freed and the function returns NULL to indicate failure. However, the BIO chain is not properly cleaned up during this error handling process.

The BIO passed by the caller retains internal pointers to the previously freed filter BIO. If the caller then calls BIO_pop() on the BIO (a common pattern in error handling code), a use-after-free occurs. This scenario directly manifests in the internal function B64_write_ASN1() which may cause BIO_new_NDEF() to be called and will subsequently call BIO_pop() on the BIO.

Root Cause

The root cause is improper memory management during error handling in the BIO_new_NDEF function. When an error occurs and the newly allocated filter BIO is freed, the function fails to properly detach the freed BIO from the chain or clear the pointers in the caller's BIO that reference the freed memory. This violates the principle of maintaining consistent state during error recovery and creates a dangling pointer scenario.

Attack Vector

The vulnerability can be triggered remotely over a network without requiring authentication or user interaction. An attacker can exploit this by providing malformed or invalid cryptographic data (such as an invalid CMS recipient public key) to applications that process SMIME, CMS, or PKCS7 content using the affected OpenSSL functions.

Public API functions that may be exploited include:

• PEM_write_bio_ASN1_stream
• PEM_write_bio_CMS_stream
• PEM_write_bio_PKCS7_stream
• SMIME_write_ASN1
• SMIME_write_CMS
• SMIME_write_PKCS7
• i2d_ASN1_bio_stream
• BIO_new_CMS
• BIO_new_PKCS7
• i2d_CMS_bio_stream
• i2d_PKCS7_bio_stream

The OpenSSL cms and smime command line applications are also affected by this vulnerability.

Detection Methods for CVE-2023-0215

Indicators of Compromise

• Unexpected crashes or core dumps in applications using OpenSSL for SMIME, CMS, or PKCS7 operations
• Application crash signatures indicating use-after-free in BIO-related functions
• Abnormal termination of services processing encrypted email or signed content
• Memory access violation errors in logs related to OpenSSL function calls

Detection Strategies

• Implement application crash monitoring for processes using OpenSSL cryptographic functions
• Deploy memory sanitizers (AddressSanitizer) in development and staging environments to detect use-after-free conditions
• Monitor system logs for segmentation faults or access violations in services handling SMIME/CMS/PKCS7 content
• Use vulnerability scanning tools to identify systems running vulnerable OpenSSL versions

Monitoring Recommendations

• Enable comprehensive logging for applications processing cryptographic content
• Configure crash dump collection and analysis for rapid incident response
• Implement service availability monitoring for critical systems using OpenSSL
• Track OpenSSL version inventory across all systems for patch management

How to Mitigate CVE-2023-0215

Immediate Actions Required

• Inventory all systems and applications using OpenSSL to identify vulnerable deployments
• Prioritize patching of internet-facing services and systems processing untrusted SMIME/CMS/PKCS7 content
• Apply vendor patches as they become available from your operating system or application vendors
• Review the OpenSSL Security Advisory 2023-02-07 for specific version guidance

Patch Information

OpenSSL has released patches addressing this vulnerability. Organizations should upgrade to patched versions as indicated in the official security advisory. The following resources provide patch details:

• OpenSSL Security Advisory
• OpenSSL Git Commit (8818064)
• OpenSSL Git Commit (9816136)
• OpenSSL Git Commit (c3829dd)

Additional vendor advisories are available from Gentoo, NetApp, and SonicWall.

Workarounds

• Restrict or disable processing of untrusted SMIME, CMS, or PKCS7 content until patches can be applied
• Implement input validation to reject malformed cryptographic data before it reaches OpenSSL functions
• Consider using application-level sandboxing to contain potential crashes and prevent service disruption
• Deploy network-level filtering to block known malicious payloads targeting this vulnerability

# Check OpenSSL version to verify patch status
openssl version -a

# Example: Verify patched version is installed
# Expected output should show a patched version per vendor advisory