Description
CHMLib through 2bef8d0, as used in SumatraPDF and other products, has a chm_lib.c _chm_decompress_block integer overflow. There is a resultant heap-based buffer overflow in _chm_fetch_bytes.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| CHMLib | CHMLib | — | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | chmlib | No fix yet | — |
| Ubuntu 26.04 LTS | chmlib | No fix yet | — |
| Ubuntu 25.10 | chmlib | No fix yet | — |
| Ubuntu 24.04 LTS | chmlib | No fix yet | — |
| Ubuntu 22.04 LTS | chmlib | No fix yet | — |
Show 3 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 20.04 LTS | chmlib | No fix yet | — |
| Ubuntu 18.04 LTS | chmlib | No fix yet | — |
| Ubuntu 16.04 LTS | chmlib | No fix yet | — |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | chmlib | 0.40-26.1 | openSUSE-SU-2025:15326-1 |
Advisories 1
- openSUSE-SU-2025:15326-1 chmlib-devel-0.40-26.1 on GA media SUSE / openSUSE Security Updates · Mar 23, 2026
References
- https://drive.google.com/file/d/1XpulFyCGlq7Szzg5RsH-eRwZ6OyuSozl/view?usp=sharing
- https://drive.google.com/file/d/1wq51px42eoJz2VQ1Qu9ObPVQVom9T9H_/view?usp=sharing
- https://github.com/jedwing/CHMLib/blob/2bef8d063ec7d88a8de6fd9f0513ea42ac0fa21f/src/chm_lib.c#L1386
- https://github.com/sumatrapdfreader/sumatrapdf/commit/08179946a745cf1605e4b9670942ec1a6e1f4c5d