OpenSSL Stack Buffer Overflows Threaten Siemens Products with DoS and Code Execution Risks

Summary

A series of vulnerabilities have been identified in OpenSSL versions 3.0 through 3.6, posing significant risks due to stack buffer overflows. These issues can lead to Denial of Service and potentially allow remote code execution if exploited successfully. The most critical vulnerability (CVE-2025-15467) affects the parsing of CMS AuthEnvelopedData or EnvelopedData messages with AEAD ciphers like AES-GCM, where oversized Initialization Vectors (IVs) can cause stack-based out-of-bounds writes. OpenSSL 1.1.1 and 1.0.2 are not impacted by these vulnerabilities.

What Happened

OpenSSL's recent security advisories have highlighted multiple vulnerabilities affecting versions 3.0 through 3.6. The most severe issue, CVE-2025-15467, involves a stack buffer overflow during the parsing of CMS AuthEnvelopedData or EnvelopedData messages with AEAD ciphers such as AES-GCM. Attackers can exploit this by crafting CMS messages with oversized IVs, leading to potential Denial of Service and remote code execution.

Technical Details

The vulnerability arises when OpenSSL parses CMS (Auth)EnvelopedData structures using AEAD ciphers. The Initialization Vector (IV), encoded in the ASN.1 parameters, is copied into a fixed-size stack buffer without verifying its length against the destination size. This oversight allows attackers to craft messages with oversized IVs, causing a stack-based out-of-bounds write before any authentication or tag verification occurs.

• CVE-2025-15467: Stack buffer overflow in CMS (Auth)EnvelopedData parsing.
  • Impact: Denial of Service and potential remote code execution.
  • Affected Versions: OpenSSL 3.6, 3.5, 3.4, 3.3, and 3.0.

Other identified vulnerabilities include:

• CVE-2025-11187: Improper validation of PBMAC1 parameters in PKCS#12 MAC verification, leading to stack-based buffer overflow or NULL pointer dereference.
• CVE-2025-15468: NULL dereference in SSL_CIPHER_find() function on unknown cipher ID, causing Denial of Service.
• CVE-2025-15469: "openssl dgst" command-line tool truncates inputs >16MB silently when using one-shot signing algorithms.
• CVE-2025-66199: TLS 1.3 CompressedCertificate excessive memory allocation.

Affected Products and Fixed Versions

OpenSSL versions 3.6, 3.5, 3.4, 3.3, and 3.0 are vulnerable to these issues. Users of these versions should upgrade as follows:

• OpenSSL 3.6: Upgrade to OpenSSL 3.6.1.
• OpenSSL 3.5: Upgrade to OpenSSL 3.5.5.
• OpenSSL 3.4: Upgrade to OpenSSL 3.4.4.
• OpenSSL 3.3: Upgrade to OpenSSL 3.3.6.
• OpenSSL 3.0: Upgrade to OpenSSL 3.0.19.

OpenSSL versions 1.1.1 and 1.0.2 are not affected by these vulnerabilities.

Exploitation Status

The exploitation of CVE-2025-15467, the most severe vulnerability, depends on platform and toolchain mitigations. However, the risk is significant due to the potential for remote code execution. The other vulnerabilities primarily lead to Denial of Service, with varying degrees of severity and exploitability.

Indicators of Compromise

No specific indicators of compromise (IOCs) have been publicly disclosed for these vulnerabilities. Organizations should monitor for unusual activity related to OpenSSL usage and be alert for any signs of exploitation attempts.

Detection Opportunities

Organizations can detect potential exploitation by monitoring for:

• Unusual network traffic patterns.
• Unexpected crashes or Denial of Service incidents in applications using affected OpenSSL versions.
• Attempts to parse malformed CMS or PKCS#12 files.

Implementing intrusion detection systems (IDS) and security information and event management (SIEM) solutions can help identify suspicious activities related to these vulnerabilities.

Timeline

• 11th September 2025: CVE-2025-11187 reported by Stanislav Fort.
• 14th October 2025: Independently reported by Hamza.
• 13th December 2025: CVE-2025-15468 and CVE-2025-15469 reported by Stanislav Fort.
• 14th December 2025: CVE-2025-15467 reported by Stanislav Fort, with additional findings on 10th February 2026.

Why This Matters for Defenders

These vulnerabilities highlight the critical importance of timely patch management and monitoring for unusual activities. Organizations using affected OpenSSL versions must prioritize upgrading to mitigate the risks of Denial of Service and potential remote code execution.

What Remains Unclear

While the technical details of these vulnerabilities are well-documented, the extent of active exploitation in the wild remains unclear. Further information on specific attack vectors and real-world incidents may emerge as more organizations assess their exposure.

Defender Guidance

Defenders should take immediate action to mitigate these vulnerabilities:

1. Upgrade OpenSSL: Ensure all instances of OpenSSL 3.0 through 3.6 are upgraded to the latest patched versions.
2. Monitor for Anomalies: Implement monitoring solutions to detect unusual network traffic and application behavior.
3. Review Security Policies: Reassess security policies related to certificate management and encryption protocols.
4. Conduct Vulnerability Assessments: Regularly perform vulnerability assessments to identify and address potential weaknesses.

By following these steps, organizations can significantly reduce their risk exposure to these OpenSSL vulnerabilities.