CVE-2022-40008

What it actually does

Heap buffer overflow in the readU8 function at lib/ttf.c allows out-of-bounds memory writes when parsing malformed TrueType font data embedded in SWF files, leading to memory corruption.

Why it matters to the business

Organizations relying on SWFTools for processing untrusted SWF files risk remote code execution and full system compromise; the issue persists unpatched across all releases with low but rising exploit interest.

How an attack unfolds

An attacker supplies a crafted SWF containing a malformed TTF font; when SWFTools invokes readU8 during font parsing the overflow corrupts heap metadata, enabling control of instruction pointer and arbitrary code execution.

How to fix it

No fixed versions exist; replace SWFTools with a maintained alternative, restrict processing to trusted inputs only, or apply a manual patch that adds bounds checking inside readU8 before any read operation.

How to confirm the fix worked

Review lib/ttf.c around commit 772e55a for absence of length validation in readU8, then fuzz the binary with malformed TTF inputs and confirm absence of crashes or memory errors after any applied fix.

Typical attack path

1. Craft malicious SWF file embedding oversized or invalid TTF data targeting readU8
2. Deliver the file to a system running vulnerable SWFTools (web upload, email attachment, automated pipeline)
3. Trigger processing of the file via any SWFTools utility that loads TTF fonts
4. Exploit resulting heap corruption to achieve code execution and persist or exfiltrate data

How to detect it

Search process execution logs and crash reports for SWFTools utilities handling TTF data; inspect for segmentation faults, heap corruption messages, or abnormal memory allocations during font parsing.

What your security team should do

• Immediately stop processing untrusted SWF or TTF content with SWFTools
• Inventory all internal uses of SWFTools and schedule removal or replacement
• Add SWFTools binaries to application allow-lists only with strict input sanitization
• Monitor upstream repositories and security lists for any community patch or fork