CVE-2026-112895: Pillow: Unbounded recursion parsing a PDF page tree or trailer chain (incomplete fix for CVE-2026-42310)
Pillow is a Python imaging library. From 5.1.0 until 13.0.0, Pillow can exhaust resources while parsing an existing PDF during an append operation. PdfParser follows page-tree child references without cycle or duplication tracking and follows previous-trailer chains with only an exact repeated-offset guard, so deep or cyclic page trees and long chains of unique trailer offsets can exhaust the Python stack. Repeated non-cyclic /Kids references can also cause super-linear CPU and memory use. An attacker can supply such a PDF to an application that calls Image.save with PDF append enabled. This can raise an uncaught RecursionError or consume excessive CPU and memory before output is written, causing denial of service. This issue is fixed in version 13.0.0.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Pillowto a version that resolves this vulnerability.Fixed in 13.0.0
Event History
Frequently Asked Questions
Which applications are exposed to this denial-of-service issue?
Applications using Pillow versions 5.1.0 through 12.x are exposed when they accept an attacker-supplied existing PDF and call Image.save with PDF append enabled. The issue affects parsing of that existing PDF during the append operation.
What does an attacker need to provide?
An attacker needs to supply a crafted PDF containing a deep or cyclic page tree, repeated non-cyclic /Kids references, or a long previous-trailer chain with unique offsets. No privileges or user interaction are indicated by the supplied CVSS vector.
What is the operational impact of successful exploitation?
Processing the crafted PDF can raise an uncaught RecursionError or consume excessive CPU and memory before output is written. This can deny service to the process handling the append operation.
What should be done if immediate upgrading is not possible?
Do not perform PDF append operations on untrusted existing PDFs until Pillow can be updated. The provided data identifies version 13.0.0 as the fixed version.