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.
Published: 2026-07-14
Score: 8.2 High
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

Impact

Pillow, a widely used Python imaging library, contains a heap out‑of‑bounds write caused by an integer overflow in the native function ImagingExpand. When the public RankFilter API receives a very large odd filter size, it expands the image before validating the size, and the unchecked signed integer arithmetic in ImagingExpand computes output dimensions that overflow. This flaw is a classic out‑of‑bounds write (CWE‑787) that can corrupt memory and potentially allow an attacker to execute arbitrary code. The underlying integer overflow (CWE‑190) is the root cause that enables the out‑of‑bounds write.

Affected Systems

The vulnerability affects all releases of Pillow older than version 12.3.0. Any Python application that imports Pillow and invokes ImageFilter.RankFilter with untrusted image data before the fix is at risk.

Risk and Exploitability

The flaw carries a CVSS score of 8.2, indicating high severity. The EPSS score is below 1 %, indicating a low probability of exploitation in the wild, and the vulnerability is not currently listed in CISA’s KEV catalog. The attack vector is inferred to be the processing of untrusted image data via the public RankFilter API; if an application processes user‑supplied images, the vulnerability is remotely exploitable. No public exploits have been reported, but the memory corruption could lead to arbitrary code execution on the host executing the image processing.

Generated by OpenCVE AI on July 31, 2026 at 09:56 UTC.

Remediation

No vendor fix or workaround currently provided.

OpenCVE Recommended Actions

  • Upgrade Pillow to version 12.3.0 or later. This patch removes the integer overflow and eliminates the heap write.
  • Validate or constrain the filter size used with RankFilter, rejecting odd sizes that exceed a safe threshold before calling the API. This mitigates the risk without requiring a library upgrade.
  • If upgrading is not immediately possible, isolate image processing in a sandboxed environment or run it in a lower‑privilege process to limit the impact of a potential exploitation.

Generated by OpenCVE AI on July 31, 2026 at 09:56 UTC.

Tracking

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-xj96-63gp-2gmr Pillow: Heap out-of-bounds write in `ImageFilter.RankFilter` via integer overflow in `ImagingExpand`
History

Tue, 21 Jul 2026 19:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Fri, 17 Jul 2026 00:15:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

 threat_severity

Important

Tue, 14 Jul 2026 17:45:00 +0000

Type Values Removed Values Added
First Time appeared Python-pillow
Python-pillow pillow
Vendors & Products Python-pillow
Python-pillow pillow

Tue, 14 Jul 2026 16:45:00 +0000

Type Values Removed Values Added
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.
Title Pillow: Heap out-of-bounds write in Pillow `ImageFilter.RankFilter` via integer overflow in `ImagingExpand`
Weaknesses CWE-190
CWE-787
References
Metrics cvssV3_1

{'score': 8.2, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H'}

Subscriptions

Python-pillow Pillow
cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-07-21T18:50:40.019Z

Reserved: 2026-07-02T19:53:48.831Z

Link: CVE-2026-59197

cve-icon Vulnrichment

Updated: 2026-07-21T18:50:15.480Z

cve-icon NVD

No data.

cve-icon Redhat

Severity : Important

Publid Date: 2026-07-14T16:25:23Z

Links: CVE-2026-59197 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-07-31T10:00:05Z

Weaknesses