[PR #1980] Fix OOB read/write in Teletext G0 charset remapping

**Original Pull Request:** https://github.com/CCExtractor/ccextractor/pull/1980 **State:** closed **Merged:** Yes --- **In raising this pull request, I confirm the following (please check boxes):** - [x] I have read and understood the [contributors guide](https://github.com/CCExtractor/ccextractor/blob/master/.github/CONTRIBUTING.md). - [x] I have checked that another pull request for this purpose does not exist. - [x] I have considered, and confirmed that this submission will be valuable to others. - [x] I accept that this submission may not be used, and the pull request closed at the will of the maintainer. - [x] I give this submission freely, and claim no ownership to its content. - [x] I have mentioned this change in the [changelog](https://github.com/CCExtractor/ccextractor/blob/master/docs/CHANGES.TXT). **My familiarity with the project is as follows (check one):** - [ ] I have never used CCExtractor. - [ ] I have used CCExtractor just a couple of times. - [ ] I absolutely love CCExtractor, but have not contributed previously. - [x] I am an active contributor to CCExtractor. ### Summary This PR fixes an out-of-bounds read/write in the Teletext decoder, specifically in the function `remap_g0_charset(uint8_t c)`. ### Root Cause - The input value `c` was used as an index into `G0_LATIN_NATIONAL_SUBSETS_MAP` (size 56) without bounds checking. - The resulting value `m` was then used as an index into another table (size 14) without validation. - Malformed input could trigger out-of-bounds reads/writes, potentially corrupting global tables. ### Fix - Added bounds checks for both `c` and `m`. - Added early returns to prevent unsafe memory access. ### Impact - Prevents memory corruption on malformed Teletext input. - Maintains decoder stability without affecting normal operation. fixed Issue: #1979

claunia commented

2026-01-29 17:23:52 +00:00

Owner

Original Pull Request: https://github.com/CCExtractor/ccextractor/pull/1980

State: closed
Merged: Yes

In raising this pull request, I confirm the following (please check boxes):

I have read and understood the contributors guide.
I have checked that another pull request for this purpose does not exist.
I have considered, and confirmed that this submission will be valuable to others.
I accept that this submission may not be used, and the pull request closed at the will of the maintainer.
I give this submission freely, and claim no ownership to its content.
I have mentioned this change in the changelog.

My familiarity with the project is as follows (check one):

I have never used CCExtractor.
I have used CCExtractor just a couple of times.
I absolutely love CCExtractor, but have not contributed previously.
I am an active contributor to CCExtractor.

Summary

This PR fixes an out-of-bounds read/write in the Teletext decoder, specifically in the function remap_g0_charset(uint8_t c).

Root Cause

The input value c was used as an index into G0_LATIN_NATIONAL_SUBSETS_MAP (size 56) without bounds checking.
The resulting value m was then used as an index into another table (size 14) without validation.
Malformed input could trigger out-of-bounds reads/writes, potentially corrupting global tables.

Fix

Added bounds checks for both c and m.
Added early returns to prevent unsafe memory access.

Impact

Prevents memory corruption on malformed Teletext input.
Maintains decoder stability without affecting normal operation.

fixed Issue: #1979

claunia added the pull-request label 2026-01-29 17:23:52 +00:00

[PR #1980] Fix OOB read/write in Teletext G0 charset remapping #2783

Summary

Root Cause

Fix

Impact