CVE-2014-4975

What it actually does

Off-by-one error in the encodes function in pack.c triggers a stack-based buffer overflow when processing certain format string specifiers, resulting in a segmentation fault.

Why it matters to the business

Unexpected crashes in Ruby-based applications can interrupt services and require manual restarts, increasing operational overhead especially in environments still running unpatched 1.9.3 or 2.x releases.

How an attack unfolds

An attacker supplies a malicious format string containing specific specifiers to a Ruby application that invokes pack, overflowing the stack buffer and forcing a segmentation fault that terminates the process.

How to fix it

Upgrade Ruby to a version newer than 2.1.2 that contains the fix for the encodes function; apply vendor patches for affected Linux distributions and recompile or reinstall dependent applications.

How to confirm the fix worked

Verify installed Ruby version is newer than 2.1.2, then test pack operations with known triggering format specifiers to confirm absence of segfaults.

Typical attack path

1. Locate a Ruby application or service that accepts attacker-controlled input for pack format strings
2. Craft a format string that triggers the off-by-one condition
3. Deliver the payload via network request or local input
4. Cause the process to segfault and deny service

How to detect it

Review system and application logs for segmentation fault entries associated with Ruby processes; correlate with inbound requests containing pack format strings around the time of crashes.

What your security team should do

• Prioritize patching Ruby across all affected systems given the age of the flaw and continued presence in legacy deployments
• Audit application code for use of pack with untrusted format strings and replace with safe alternatives
• Implement runtime monitoring for Ruby process crashes and segment faults