CVE-2021-42201

What it actually does

Heap-buffer-overflow in swf_GetD64 within rfxswf.c allows local code execution via crafted input.

Why it matters to the business

Enables full system compromise on affected hosts when users process malicious files, increasing breach and ransomware risk despite low EPSS and no KEV listing; limited downstream prevalence reduces widespread operational disruption.

How an attack unfolds

Attacker supplies a malicious input file that triggers the overflow in the vulnerable parsing function, achieving arbitrary code execution on the local system; public exploit code is available but no named threat actors are associated.

How to fix it

Upgrade libp2p/js-libp2p to commit 29c803a63e5aacda1e5b87527b15bf27b31ea5a6; rebuild and redeploy all dependent packages.

How to confirm the fix worked

Confirm the fixed commit is present in source, run regression tests against known overflow vectors, and verify no heap overflows occur with sanitizers.

Typical attack path

1. Craft malicious input file exploiting the heap overflow
2. Deliver file to target via email, download, or shared storage
3. Victim opens or processes the file with the vulnerable library
4. Overflow triggers and executes attacker-controlled code

How to detect it

Review application crash logs and memory sanitizer reports for heap overflows during SWF or related file processing; correlate with file open events in user activity logs.

What your security team should do

• Apply the listed commit upgrade across all libp2p/js-libp2p instances within 30 days
• Scan build pipelines and dependency manifests for the vulnerable version
• Monitor EPSS trend for any acceleration and prepare emergency patching if exploit usage rises