CVE-2026-59197
Description
A flaw was found in Pillow prior to 12.3.0. The public RankFilter API can trigger a native heap out-of-bounds write when given a very large odd filter size. ImageFilter.RankFilter.filter() calls image.expand(size // 2, size // 2) before rank-filter size validation, and ImagingExpand() computes output dimensions with unchecked signed integer arithmetic. This can lead to denial of service and limited integrity impact via heap corruption.
Statement
Pillow's RankFilter API is vulnerable to a native heap out-of-bounds write when a caller supplies a very large odd filter size. Expansion runs before size validation and ImagingExpand uses unchecked signed integer arithmetic for output dimensions. A remote attacker who can drive RankFilter with attacker-controlled sizes may crash the process or corrupt heap memory. Fixed in Pillow 12.3.0.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 8.2 | N/A | 8.2 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | Low | N/A | Low |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
Understanding the Weakness (CWE)
Integrity
Technical Impact: Modify Memory; Execute Unauthorized Code or Commands
Write operations could cause memory corruption. In some cases, an adversary can modify control data such as return addresses in order to execute unexpected code.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
Attempting to access out-of-range, invalid, or unauthorized memory could cause the product to crash.
Other
Technical Impact: Unexpected State
Subsequent write operations can produce undefined or unexpected results.
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