CVE-2025-9230: OpenSSL CMS Encryption DoS Vulnerability

CVE-2025-9230 Overview

CVE-2025-9230 is a memory corruption vulnerability in OpenSSL affecting applications that decrypt CMS (Cryptographic Message Syntax) messages using password-based encryption. When processing specially crafted CMS messages, the vulnerability can trigger an out-of-bounds read and write condition in memory, potentially leading to application crashes or arbitrary code execution.

The vulnerability exists in the CMS message decryption functionality when handling password-based recipient information (PWRI). While the probability of successful exploitation is considered low due to the complexity involved and the limited use of PWRI encryption in practice, the potential consequences of a successful attack are severe, ranging from Denial of Service to remote code execution.

Critical Impact

Successful exploitation of this vulnerability can result in memory corruption leading to Denial of Service through application crashes, or potentially allow attackers to execute arbitrary code on affected systems processing malicious CMS messages.

Affected Products

• OpenSSL versions with CMS password-based encryption support
• Applications using OpenSSL's CMS decryption functionality with PWRI
• Note: FIPS modules in versions 3.0, 3.1, 3.2, 3.3, 3.4, and 3.5 are not affected as CMS implementation is outside the FIPS module boundary

Discovery Timeline

• September 30, 2025 - CVE-2025-9230 published to NVD
• November 4, 2025 - Last updated in NVD database

Technical Details for CVE-2025-9230

Vulnerability Analysis

This vulnerability is classified as CWE-125 (Out-of-Bounds Read), though the issue also involves out-of-bounds write conditions. The flaw occurs during the decryption process of CMS messages that utilize password-based encryption (PWRI). When an application attempts to decrypt a maliciously crafted CMS message, improper bounds checking in the decryption routine allows memory access beyond the intended buffer boundaries.

The out-of-bounds read can expose sensitive memory contents or trigger crashes when accessing unmapped memory regions. More critically, the out-of-bounds write component can corrupt adjacent memory structures, potentially allowing an attacker to modify control flow data or inject malicious code.

It's worth noting that PWRI encryption support in CMS messages is rarely used in production environments, which significantly reduces the attack surface for this vulnerability. Additionally, the FIPS-validated modules in OpenSSL 3.x versions remain unaffected because the CMS implementation resides outside the FIPS module boundary.

Root Cause

The root cause of CVE-2025-9230 lies in insufficient boundary validation when processing CMS messages with password-based recipient information. During the decryption operation, the code fails to properly validate the size of input data against buffer boundaries before performing read and write operations. This allows a specially crafted CMS message to manipulate memory operations beyond allocated buffer regions.

Attack Vector

The attack vector for this vulnerability is network-based, requiring no authentication or user interaction. An attacker must craft a malicious CMS message using password-based encryption and deliver it to a vulnerable application for decryption processing.

The attack scenario involves:

1. An attacker crafts a malicious CMS message with manipulated PWRI encryption parameters
2. The malicious message is sent to a target application that processes CMS-encrypted content
3. When the application attempts to decrypt the message using password-based decryption, the vulnerability is triggered
4. The out-of-bounds memory access can cause immediate application crash (DoS) or, in more sophisticated attacks, enable code execution through memory corruption

The vulnerability can be exploited without prior knowledge of the decryption password, as the memory corruption occurs during the decryption preparation phase before password validation.

Detection Methods for CVE-2025-9230

Indicators of Compromise

• Unexpected application crashes in services handling CMS message decryption
• Segmentation faults or memory access violations in OpenSSL-linked processes
• Anomalous CMS-encrypted messages in network traffic with unusual PWRI parameters
• Memory corruption indicators in application logs or crash dumps related to CMS operations

Detection Strategies

• Deploy application monitoring to detect crashes or abnormal behavior in services processing CMS messages
• Implement network inspection rules to identify malformed CMS message structures targeting PWRI encryption
• Monitor system logs for segmentation faults or memory errors in OpenSSL-dependent applications
• Use SentinelOne's behavioral analysis to detect exploitation attempts and memory corruption patterns

Monitoring Recommendations

• Enable crash monitoring and automatic restart policies for applications using OpenSSL CMS functionality
• Configure logging to capture detailed error information when CMS decryption failures occur
• Implement memory protection mechanisms such as ASLR and stack canaries to detect exploitation attempts
• Review network traffic for unusual CMS message patterns, particularly those using password-based encryption

How to Mitigate CVE-2025-9230

Immediate Actions Required

• Inventory all systems and applications using OpenSSL with CMS message processing capabilities
• Apply the latest OpenSSL security patches to all affected systems immediately
• If patching is not immediately possible, disable or restrict CMS password-based encryption functionality
• Monitor applications for signs of exploitation or unusual CMS processing behavior

Patch Information

OpenSSL has released patches to address this vulnerability. The fixes are available through multiple commits in the OpenSSL repository:

• OpenSSL commit 5965ea5
• OpenSSL commit 9e91358
• OpenSSL commit a79c4ce
• OpenSSL commit b5282d6
• OpenSSL commit bae259a

Extended release patches are also available through the OpenSSL Extended Releases repository.

For complete details, refer to the OpenSSL Security Advisory and the Debian LTS Announcement.

Workarounds

• Disable CMS password-based encryption (PWRI) functionality if not required for business operations
• Implement network-level filtering to block or inspect CMS-encrypted messages before they reach vulnerable applications
• Use application firewalls to validate CMS message structure before processing
• Isolate applications that must process CMS messages with PWRI in restricted network segments with enhanced monitoring

# Check OpenSSL version on affected systems
openssl version -a

# Verify OpenSSL package version on Debian/Ubuntu systems
dpkg -l | grep openssl

# Update OpenSSL to patched version (example for Debian/Ubuntu)
apt-get update && apt-get upgrade openssl