CVE-2024-22956

What it actually does

Heap use-after-free in the removeFromTo function allows memory corruption when processing specially crafted SWF input.

Why it matters to the business

Systems that parse untrusted SWF files with this library face elevated risk of crashes or full host compromise, with no vendor patch available after nearly three years.

How an attack unfolds

An attacker supplies a malicious SWF file that reaches the removeFromTo code path, triggering the use-after-free to corrupt heap metadata and achieve arbitrary code execution.

How to fix it

Remove or isolate swftools 0.9.2 from all build and runtime environments; replace with an alternative SWF processing library or maintain the component offline until a patched release appears.

How to confirm the fix worked

Confirm the installed swftools version is not 0.9.2, verify the swfc binary does not contain the vulnerable removeFromTo symbol at the reported offset, and test sample inputs in an isolated environment.

Typical attack path

1. Craft a malicious SWF file that exercises the vulnerable code path in swfc.c
2. Deliver the file to a target that invokes swftools utilities (swfc, swfcombine, etc.)
3. Trigger the removeFromTo function to cause the use-after-free
4. Leverage the resulting memory corruption for code execution or denial of service

How to detect it

Review process execution logs and command-line history for swfc or other swftools binaries run against external or untrusted SWF files; look for segmentation faults or heap-related crashes in those processes.

What your security team should do

• Inventory all instances of swftools and block its execution on production systems
• Add swftools to the organization's disallowed-software list
• Monitor upstream repositories for any future fixed release and reassess
• Scan historical logs for invocations of swfc or related binaries on untrusted input