CVE-2015-2806

What it actually does

Stack-based buffer overflow in the asn1_der_decoding function allows an attacker to write beyond allocated stack memory when processing malformed ASN.1 DER input.

Why it matters to the business

Remote attackers could gain full control of affected systems that parse untrusted ASN.1 data, leading to widespread compromise of services relying on this library across Linux distributions and dependent applications.

How an attack unfolds

An attacker crafts a malicious ASN.1 DER structure and supplies it to any application using the vulnerable libtasn1 library for decoding; the overflow occurs during asn1_der_decoding, potentially allowing arbitrary code execution or denial of service with no authentication required.

How to fix it

Upgrade libtasn1 to version 4.4 or later on all affected systems; rebuild and redeploy any dependent packages after the library update.

How to confirm the fix worked

Verify installed libtasn1 version is 4.4 or higher using package manager queries or library file inspection; test decoding of known-good and boundary ASN.1 DER inputs to confirm stability.

Typical attack path

1. Identify a network service or application that accepts ASN.1 DER input and links against vulnerable libtasn1
2. Craft a specially formatted DER payload that triggers the stack overflow in asn1_der_decoding
3. Transmit the payload over the network or via a file processed by the target
4. Achieve remote code execution or crash the process

How to detect it

Review application logs and process crash dumps for unexpected terminations or segmentation faults during ASN.1 parsing; correlate with network traffic containing unusual DER structures around the time of the event.

What your security team should do

• Immediately inventory all systems for libtasn1 versions older than 4.4
• Prioritize patching on internet-facing systems and those handling certificates or cryptographic material
• Monitor vendor advisories for downstream package updates in Ubuntu, Debian, and Fedora
• Apply compensating controls such as input validation or sandboxing where upgrades are delayed