CVE-2026-59197

Pillow: Heap out-of-bounds write in Pillow `ImageFilter.RankFilter` via integer overflow in `ImagingExpand`

Published Jul 14, 2026 CVSS 3.1 · 8.2 High EPSS < 1% KEV · Not listed

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.

Analysis

Technical 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.

Affected Products

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

python-pillow

Pillow

affected

Version	Status	Constraints
`< 12.3.0`	affected	—

Configuration 1 [-]

cpe:2.3:a:python:pillow:*:*:*:*:*:*:*:*

No data.

Vendor Product Versions

Python-pillow

Pillow

Version	Status	Scheme	Platform
`[0,12.3.0)`	affected	semver	—

Remediation

No solution or workaround provided in the CVE record.

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

Advisories

Source	ID	Title
Github GHSA	GHSA-xj96-63gp-2gmr	Pillow: Heap out-of-bounds write in `ImageFilter.RankFilter` via integer overflow in `ImagingExpand`
Ubuntu USN	USN-8999-1	Pillow vulnerabilities

Metrics

No CVSS v4.0

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact Low

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

Exploit prediction score: < 1% (0.445% probability within 30 days)

Exploitation poc

Automatable yes

Technical Impact partial

References

Link	Providers
https://github.com/python-pillow/Pillow/commit/cce3bdb867c77a3420261ed1bfdb6b0787ec8fc1
https://github.com/python-pillow/Pillow/pull/9695
https://github.com/python-pillow/Pillow/releases/tag/12.3.0
https://github.com/python-pillow/Pillow/security/advisories/GHSA-xj96-63gp-2gmr
https://nvd.nist.gov/vuln/detail/CVE-2026-59197
https://www.cve.org/CVERecord?id=CVE-2026-59197

History

Jul 21, 2026 7:30 PM Scoring metrics updated View changes

Type	Values Removed	Values Added
Metrics		ssvc `{'options': {'Automatable': 'yes', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}`

Jul 17, 2026 12:15 AM Added references. Scoring metrics updated View changes

Type	Values Removed	Values Added
References		https://nvd.nist.gov/vuln/detail/CVE-2026-59197 https://www.cve.org/CVERecord?id=CVE-2026-59197
Metrics	threat_severity `None`	threat_severity `Important`

Jul 14, 2026 5:45 PM First appearance in the feed. Affected vendors updated View changes

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

Jul 14, 2026 4:45 PM Description updated. Title updated. Weaknesses updated. Added references. Scoring metrics updated View changes

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		https://github.com/python-pillow/Pillow/commit/cce3bdb867c77a3420261ed1bfdb6b0787ec8fc1 https://github.com/python-pillow/Pillow/pull/9695 https://github.com/python-pillow/Pillow/releases/tag/12.3.0 https://github.com/python-pillow/Pillow/security/advisories/GHSA-xj96-63gp-2gmr
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'}`