CVE-2015-7181

What it actually does

The sec_asn1d_parse_leaf function in NSS improperly restricts access to a data structure when processing crafted OCTET STRING data, resulting in a use-after-poison memory corruption condition that can crash the application or allow arbitrary code execution.

Why it matters to the business

Applications relying on the vulnerable NSS library may experience unexpected crashes or full system compromise, disrupting services and potentially allowing attackers to execute malicious code on affected systems.

How an attack unfolds

An attacker crafts a malicious ASN.1 OCTET STRING payload and delivers it over the network to a target application using the vulnerable NSS library, triggering the use-after-poison flaw during parsing to either crash the process or gain arbitrary code execution.

How to fix it

Upgrade affected packages to the fixed versions: linux (Debian:11,12,13) to 4.9.25-1; linux-hwe (Ubuntu:16.04:LTS) to 4.8.0-52.55~16.04.1. Rebuild or redeploy any dependent applications after the library update.

How to confirm the fix worked

Verify the installed NSS or package version matches or exceeds the listed fixed versions on each system; test ASN.1 parsing paths with known-good inputs to confirm stability.

Typical attack path

1. Identify a target application or service using vulnerable NSS for ASN.1 or TLS processing
2. Craft and send a malicious OCTET STRING within ASN.1 data to the target
3. Trigger parsing in sec_asn1d_parse_leaf to induce use-after-poison
4. Achieve denial of service via crash or attempt code execution for further access

How to detect it

Review application logs and crash reports for NSS-related segmentation faults or memory errors during ASN.1 or certificate processing; examine network traffic for unusual ASN.1 structures targeting older NSS versions.

What your security team should do

• Apply the listed package upgrades immediately across all affected Debian and Ubuntu systems
• Scan environments for any remaining instances of NSS versions prior to the fixes
• Monitor for any NSS-related process crashes as a temporary indicator of exposure