Description
Pillow is a Python imaging library. From 5.4.0 until 13.0.0, Pillow performs quadratic copying while parsing GIF comments. GifImageFile._seek() repeatedly appends immutable bytes for comment sub-blocks and multiple comment extensions, and frame zero is parsed during Image.open(). An attacker can submit a small-dimension GIF containing many comment extensions to any application that opens the file. This can consume excessive CPU and deny service before the application can inspect the image. This issue is fixed in version 13.0.0.
Published: 2026-10-19
Score: 6.9 Medium
EPSS: n/a
KEV: No
Impact: Denial of Service
Action: Immediate Patch
AI Analysis

Impact

A quadratic concatenation bug in Pillow’s GIF comment parsing causes the library to repeatedly append immutable byte strings for each comment sub-block. An attacker can craft a small‑dimension GIF with many comment extensions that forces the parser to perform an exponential amount of work before Image.open() returns, consuming CPU and potentially bringing the host application to a halt before any image metadata is inspected. The flaw is a classic denial of service rather than a code‑execution issue, and it is linked to CWE‑407, Improper Resource Management.

Affected Systems

The issue affects the Python Pillow imaging library, with all releases from 5.4.0 through 13.0.0 inclusive. Installation of Pillow by name python-pillow:Pillow triggers the vulnerability during Image.open() of GIF files. The vulnerability is mitigated in Pillow 13.0.0 and later.

Risk and Exploitability

The CVSS base score of 6.9 indicates moderate severity, and the EPSS score is not available, so the current exploitation probability is unknown. The vulnerability is not listed in CISA’s KEV catalog, but the vulnerability can be exploited by any Python application that imports Pillow and processes GIF images, without requiring elevated privileges or special network exposure. The attack vector is inferred to be local or remote upload of a crafted GIF to any service using Pillow for image handling.

Generated by OpenCVE AI on October 20, 2026 at 00:20 UTC.

Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

  • Upgrade Pillow to 13.0.0 or later.
  • Replace the current Pillow package in all Python environments that handle image uploads.
  • If an immediate upgrade is not possible, validate or reject GIF files that contain an unusually large number of comment extensions before calling Image.open() to mitigate the denial‑of‑service risk.

Generated by OpenCVE AI on October 20, 2026 at 00:20 UTC.

Tracking

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Advisories

No advisories yet.

History

Tue, 20 Oct 2026 00:30:00 +0000

Type Values Removed Values Added
Weaknesses CWE-770
References
Metrics threat_severity

None

 cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L'}

threat_severity

Moderate

Mon, 19 Oct 2026 23:00:00 +0000

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

Mon, 19 Oct 2026 21:30:00 +0000

Type Values Removed Values Added
Description Pillow is a Python imaging library. From 5.4.0 until 13.0.0, Pillow performs quadratic copying while parsing GIF comments. GifImageFile._seek() repeatedly appends immutable bytes for comment sub-blocks and multiple comment extensions, and frame zero is parsed during Image.open(). An attacker can submit a small-dimension GIF containing many comment extensions to any application that opens the file. This can consume excessive CPU and deny service before the application can inspect the image. This issue is fixed in version 13.0.0.
Title Pillow: Quadratic GIF comment concatenation allows DoS in Image.open()
Weaknesses CWE-407
References
Metrics cvssV4_0

{'score': 6.9, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N'}

Subscriptions

Python-pillow Pillow
cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-10-19T21:15:21.484Z

Reserved: 2026-10-19T16:58:51.959Z

Link: CVE-2026-112401

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-10-19T22:17:07.503

Modified: 2026-10-19T22:17:07.503

Link: CVE-2026-112401

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-10-19T21:15:21Z

Links: CVE-2026-112401 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-10-20T00:30:07Z

Weaknesses
  • CWE-407

    Inefficient Algorithmic Complexity

  • CWE-770

    Allocation of Resources Without Limits or Throttling