[PR #1817] fix(rust): Add bounds checks to prevent panic on malformed CEA-708 data #2565

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claunia · 2026-01-29T17:22:47Z

claunia commented

2026-01-29 17:22:47 +00:00

Original Pull Request: https://github.com/CCExtractor/ccextractor/pull/1817

State: closed
Merged: Yes

Summary

Fixes #1616 - Segmentation fault when extracting from MP4 remuxed from HLS
Fixes #1575 - Regression bug causing ccextractor 0.94 to crash

The CEA-708 decoder could panic when processing truncated or malformed caption data blocks. This PR adds proper bounds checking to prevent panics:

Fixed EXT1 command handling in process_service_block():
- Changed &block[1..] to &block[(i+1)..] for correct slice offset when EXT1 appears at non-zero positions
- Added bounds check before accessing the next byte after EXT1
Added bounds checks in handle_extended_char():
- Check for empty block before accessing block[0]
- Check block.len() >= 2 before accessing block[1] for C3 commands
Fixed clippy warning in es/pic.rs:
- Removed unnecessary as i64 cast

Test plan

Verified with #1616 sample file (MP4 remuxed from HLS)
Verified with #1575 sample file (EIA-608 and EIA-708 streams.ts) - extracts subtitles correctly
All 268 Rust tests pass
Added 4 new unit tests for bounds checking:
- test_handle_extended_char_empty_block
- test_handle_extended_char_c3_insufficient_bytes
- test_process_service_block_ext1_at_end
- test_process_service_block_ext1_with_truncated_c3
No clippy warnings
No formatting issues

🤖 Generated with Claude Code

**Original Pull Request:** https://github.com/CCExtractor/ccextractor/pull/1817 **State:** closed **Merged:** Yes --- ## Summary Fixes #1616 - Segmentation fault when extracting from MP4 remuxed from HLS Fixes #1575 - Regression bug causing ccextractor 0.94 to crash The CEA-708 decoder could panic when processing truncated or malformed caption data blocks. This PR adds proper bounds checking to prevent panics: - **Fixed EXT1 command handling** in `process_service_block()`: - Changed `&block[1..]` to `&block[(i+1)..]` for correct slice offset when EXT1 appears at non-zero positions - Added bounds check before accessing the next byte after EXT1 - **Added bounds checks** in `handle_extended_char()`: - Check for empty block before accessing `block[0]` - Check `block.len() >= 2` before accessing `block[1]` for C3 commands - **Fixed clippy warning** in `es/pic.rs`: - Removed unnecessary `as i64` cast ## Test plan - [x] Verified with #1616 sample file (MP4 remuxed from HLS) - [x] Verified with #1575 sample file (EIA-608 and EIA-708 streams.ts) - extracts subtitles correctly - [x] All 268 Rust tests pass - [x] Added 4 new unit tests for bounds checking: - `test_handle_extended_char_empty_block` - `test_handle_extended_char_c3_insufficient_bytes` - `test_process_service_block_ext1_at_end` - `test_process_service_block_ext1_with_truncated_c3` - [x] No clippy warnings - [x] No formatting issues 🤖 Generated with [Claude Code](https://claude.com/claude-code)

claunia added the pull-request label 2026-01-29 17:22:47 +00:00

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Reference: starred/ccextractor#2565