CVE-2021-39583

What it actually does

A NULL pointer dereference in pool_lookup_string2() within pool.c crashes the process when handling malformed input during string pool operations.

Why it matters to the business

Workflows that process untrusted files with the affected software can experience sudden application failures and halted operations.

How an attack unfolds

An attacker supplies a specially crafted input file that reaches the vulnerable string lookup routine with invalid data, triggering the dereference and immediate crash on any system running the unpatched code.

How to fix it

Apply any available upstream patches to pool.c that validate pointers before dereference; if no official release exists, replace the tool with a maintained alternative or sandbox its execution to limit blast radius.

How to confirm the fix worked

Re-run the original crashing input against the updated binary and confirm the process exits cleanly without dereference; inspect source for explicit NULL checks around pool_lookup_string2 callers.

Typical attack path

1. Create a malformed input file that exercises the NULL dereference path in pool_lookup_string2
2. Deliver the file through normal channels such as email, web download, or shared storage
3. Convince the target to open or process the file with a vulnerable swftools utility
4. Trigger the crash and resulting denial of service

How to detect it

Review process crash logs and core dumps for stack traces referencing pool.c or pool_lookup_string2; correlate with file-processing events involving swftools binaries.

What your security team should do

• Remove or isolate swftools from any automated file-processing pipelines until a fixed build is obtained
• Add input sanitization and sandboxing around remaining instances
• Track upstream commits for a corrected release and test it promptly