CVE-2012-6656

What it actually does

Out-of-bounds read in iconvdata/ibm930.c during IBM930 to UTF-8 conversion when processing multibyte value 0xffff.

Why it matters to the business

Applications performing character-set conversion can crash, causing service outages or degraded availability in systems that rely on glibc iconv.

How an attack unfolds

An attacker supplies specially crafted IBM930-encoded input containing the multibyte sequence 0xffff to any application that calls iconv; the library performs an unchecked array access leading to a denial-of-service crash.

How to fix it

Upgrade GNU C Library to version 2.16 or later; rebuild and restart all dependent applications.

How to confirm the fix worked

Confirm glibc version is at least 2.16; run iconv with the test sequence 0xffff under IBM930 to UTF-8 and verify no crash occurs.

Typical attack path

1. Identify a network service or local process that invokes iconv on attacker-controlled data
2. Craft IBM930 input containing the multibyte value 0xffff
3. Deliver the payload via the service's normal data path
4. Trigger iconv conversion resulting in out-of-bounds read and process crash

How to detect it

Review application and system logs for unexpected crashes during character conversion; correlate with processes that call iconv on untrusted data.

What your security team should do

• Inventory all systems using glibc < 2.16 and schedule immediate upgrades
• Prioritize patching on internet-facing or high-availability services first
• Add glibc version checks to vulnerability scanning and patch-management processes