CVE-2021-39597

What it actually does

NULL pointer dereference in code_dump2() within code.c causes the process to crash when parsing a specially crafted SWF file.

Why it matters to the business

Attackers can crash the swftools utilities, interrupting any automated or manual workflows that convert or inspect Flash files and forcing restarts or fallback procedures.

How an attack unfolds

An attacker crafts a malformed SWF file that reaches the vulnerable code path in code_dump2; when a user or automated process opens the file with any swftools utility the dereference occurs and the program terminates.

How to fix it

Upgrade to a patched version of swftools once released; until then avoid processing untrusted SWF files with the affected utilities and consider alternative tools for Flash inspection.

How to confirm the fix worked

Confirm the installed swftools version is newer than the vulnerable 20200710 build and test that the previously crashing sample no longer causes a crash.

Typical attack path

1. Create or obtain a malicious SWF file that triggers the NULL dereference in code_dump2
2. Deliver the file via email, web download, or shared storage
3. Victim or automated scanner invokes an swftools binary on the file
4. Process crashes, resulting in denial of service

How to detect it

Review process crash logs and application execution history for unexpected terminations of swftools binaries when handling SWF input.

What your security team should do

• Block or sandbox untrusted SWF processing until a fixed build is available
• Monitor for new swftools releases and apply updates promptly
• Replace swftools usage with maintained alternatives where possible