Product overview
Product: OpenSSL
Category: Cryptographic / TLS / CMS processing library
Exposure context: Any application, service, appliance, or platform that links against vulnerable OpenSSL versions and processes CMS (S/MIME) messages or imports PKCS#12 (.p12 / .pfx) files.
The vulnerabilities described below affect core parsing logic. They are not limited to edge cases and can be triggered through malformed but valid cryptographic objects.
High-level CVE information table
| CVE Name | CVE ID | CVSS Score (approx.) | Severity | Affected Versions | Attack Vector | Exploitability | Impact | Exploit Availability |
|---|---|---|---|---|---|---|---|---|
| CMS AuthEnvelopedData stack overflow | CVE-2025-15467 | ~8.1 | High / Critical (context-dependent) | OpenSSL 3.0 – 3.6 | Remote, unauthenticated | Medium (environment dependent) | DoS, potential RCE | No public weaponized exploit (research-level PoCs may exist) |
| PKCS#12 friendlyName heap OOB write | CVE-2025-69419 (VE-2025-69419) | ~3.1 | Low | OpenSSL 1.1.1 – 3.6 | Local or remote (file-based) | Low | DoS, memory corruption | No public exploit; theoretical exploitation only |
Detailed vulnerability analysis
CVE-2025-15467
CMS AuthEnvelopedData Stack Buffer Overflow
Vulnerability type
- Stack-based buffer overflow
- Memory corruption during ASN.1 parsing
Root cause
A fixed-size stack buffer is used when parsing AEAD parameters (such as IVs) within CMS AuthEnvelopedData structures. The incoming ASN.1-encoded length is not sufficiently validated before data is copied into the stack buffer.
When a crafted CMS object declares a length larger than the destination buffer, stack memory beyond the buffer boundary is overwritten.
How exploitation could occur
Exploitation can occur wherever untrusted CMS data is parsed automatically or semi-automatically, including:
- S/MIME email processing by MTAs or secure email gateways
- Applications validating encrypted or signed CMS payloads
- Identity, messaging, or document-signing systems relying on CMS
An attacker only needs the ability to deliver a crafted CMS message. No authentication is required in typical email or gateway scenarios.
Exploitation mechanics (educational context)
- A malicious CMS AuthEnvelopedData structure is constructed with oversized AEAD parameters.
- During parsing, the length field is trusted.
- Excess data overwrites adjacent stack memory.
- The process crashes or enters undefined behavior.
On hardened systems, stack canaries or ASLR typically limit exploitation to denial-of-service. On less hardened builds, control-flow manipulation may be theoretically possible.
Impact
- Primary impact: Service crash (denial of service).
- Secondary impact: Potential remote code execution under favorable conditions.
MITRE / CWE mapping
- CWE-121: Stack-based Buffer Overflow
- CWE-787: Out-of-bounds Write
CVE-2025-69419
PKCS#12 FriendlyName Heap Out-of-Bounds Write
Vulnerability type
- Heap-based out-of-bounds write (single byte)
- Memory corruption during character encoding conversion
Root cause
When converting a BMPString friendlyName field to UTF-8, certain non-ASCII Unicode characters cause incorrect length calculation across a two-pass conversion routine. This leads to a negative return value and results in a single null byte being written just before the allocated heap buffer.
How exploitation could occur
Exploitation requires:
- Importing or parsing a malicious PKCS#12 (.p12 / .pfx) file
- Invocation of the friendlyName extraction routine
Typical exposure points include:
- Web-based certificate management interfaces
- Automated certificate enrollment systems
- Administrative tools importing user-supplied PKCS#12 files
Exploitation mechanics (educational context)
- A PKCS#12 file is crafted with a specially encoded BMPString friendlyName.
- During UTF-8 conversion, heap memory is underwritten by one byte.
- Heap metadata or adjacent memory may be corrupted.
Impact
- Primary impact: Application crash (DoS).
- Secondary impact: Extremely limited potential for code execution under contrived heap layouts.
MITRE / CWE mapping
- CWE-122: Heap-based Buffer Overflow
- CWE-787: Out-of-bounds Write
Detection and monitoring guidance
Relevant log sources
- Application logs for OpenSSL-linked services
- Mail servers and secure email gateways
- System logs capturing segmentation faults or aborts
- Core dump handlers and crash reporters
- EDR / host-based security telemetry
- Certificate import and enrollment audit logs
Indicators of exploitation or probing
- Repeated crashes shortly after processing CMS or PKCS#12 input
- ASN.1 parsing errors or CMS-related decoding failures
- Segmentation faults in processes handling email, certificates, or cryptographic payloads
- Abnormal termination correlated with inbound S/MIME messages or certificate uploads
Detection rule concepts
- Alert on segmentation faults from OpenSSL-consuming processes
- Correlate crashes with inbound CMS messages or PKCS#12 imports
- Monitor for abnormal ASN.1 length fields exceeding expected thresholds
- Flag certificate imports originating from untrusted or external sources
Payload signatures are discouraged due to fragility and high false-positive rates.
Risk evaluation
| CVE | Risk level | Reasoning |
|---|---|---|
| CVE-2025-15467 | High | Remote, unauthenticated input, stack memory corruption, potential RCE |
| CVE-2025-69419 | Low | Single-byte heap overwrite, constrained exploitation, file-based trigger |
Despite differing severity scores, both vulnerabilities represent unacceptable risk in security-sensitive environments.
Mitigation and remediation
Required action
Upgrade OpenSSL to the fixed release for the deployed version branch. This is the only complete remediation.
Compensating controls
- Restrict or sandbox CMS and PKCS#12 parsing
- Limit certificate imports to trusted administrators
- Increase crash and memory fault monitoring
- Enable additional runtime protections where supported
Official patch / upgrade link
OpenSSL Security Advisory and Fixed Versions:
👉 https://openssl-library.org/news/secadv/20260127.txt
Final takeaway
These vulnerabilities highlight the inherent risk of complex ASN.1 parsing in cryptographic libraries. Even low-severity memory corruption flaws warrant prompt remediation. Applying the official OpenSSL updates and validating dependent applications is strongly recommended across all environments.
