Security · Pillow
Saving a large DDS image overruns a heap buffer in Pillow's BCn encoder
Pillow vulnerability can cause write buffer overflow on BCn encoding
- Advisory
- CVE-2025-48379
- Library
- Pillow, pillow on PyPI
- Published
- Severity
- 7.1 out of 10, as published
- Affected
- < 11.3.0
- Fixed in
- 11.3.0
- Reaches you
- on a save path
What triggers it
Image.save(..., format="DDS") of an image larger than about 64 KB encoded, with default settings.
What sillybos does
Not reached by opening a file
Opening or reading a file never reaches this flaw, so a check before decoding has nothing to refuse. Listed so that nobody expects it to.
On the DDS save path only; Image.open never runs the BCn encoder.
Proposed from the advisory's text on 2026-11-01, as part of folding the backfill into the record; confirmed by a person on 2026-11-03.
How to protect yourself
In general. Upgrade to Pillow 11.3.0.
Specifically. Not a pre-decode matter: the flaw is on a save path.
The general advice applies to every row here.
Sources
- https://osv.dev/vulnerability/GHSA-xg8h-j46f-w952
- https://osv.dev/vulnerability/PYSEC-2025-61
- The record entry, triaged 2026-11-03, last checked 2026-11-03