High severity · published Jul 14, 2026
CVE-2026-59197
Pillow: Heap out-of-bounds write in Pillow `ImageFilter.RankFilter` via integer overflow in `ImagingExpand`
8.2
CVSS
0.4%
EPSS
No
On KEV
Description
Pillow is a Python imaging library. Prior to 12.3.0, Pillow's public rank-filter API can trigger a native heap out-of-bounds write when given a very large odd filter size because ImageFilter.RankFilter.filter() calls image.expand(size // 2, size // 2) before rank-filter size validation and ImagingExpand() computes output dimensions with unchecked signed int arithmetic. This issue is fixed in version 12.3.0.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
Low
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 39% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
PI
Pillow · python-pillow
< 12.3.0 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-59197
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-59197
Patch
https://github.com/python-pillow/Pillow/commit/cce3bdb867c77a3420261ed1bfdb6b0787ec8fc1
Issue Tracking
https://github.com/python-pillow/Pillow/pull/9695
Release Notes
https://github.com/python-pillow/Pillow/releases/tag/12.3.0
Exploit
https://github.com/python-pillow/Pillow/security/advisories/GHSA-xj96-63gp-2gmr
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