CVE-2026-96637

Pillow: Decompression bomb check bypass in SpiderImagePlugin.seek() leads to unbounded allocation DoS

Published Oct 21, 2026 CVSS 4.0 · 7.1 High EPSS < 1% KEV · Not listed
Description
Pillow is a Python imaging library. Prior to 13.0.0, SpiderImageFile.seek() in src/PIL/SpiderImagePlugin.py reparses a later SPIDER stack frame and replaces self._size without rerunning Image._decompression_bomb_check(). A tiny file can use a safe first frame to pass Image.open() and then declare very large dimensions in a later mode F frame. Loading that frame allocates approximately four bytes per attacker-declared pixel and can consume multiple gigabytes of memory. This issue is fixed in version 13.0.0.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-g842-9rc4-69pw Pillow: Decompression bomb check bypass in SpiderImagePlugin.seek() leads to unbounded allocation DoS
History
Type Values Removed Values Added
First Time appeared Python
Python pillow
CPEs cpe:2.3:a:python:pillow:*:*:*:*:*:*:*:*
Vendors & Products Python
Python pillow
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
References
Metrics threat_severity

None

cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H'}

threat_severity

Moderate

Type Values Removed Values Added
First Time appeared Python-pillow
Python-pillow pillow
Vendors & Products Python-pillow
Python-pillow pillow
Type Values Removed Values Added
Description Pillow is a Python imaging library. Prior to 13.0.0, SpiderImageFile.seek() in src/PIL/SpiderImagePlugin.py reparses a later SPIDER stack frame and replaces self._size without rerunning Image._decompression_bomb_check(). A tiny file can use a safe first frame to pass Image.open() and then declare very large dimensions in a later mode F frame. Loading that frame allocates approximately four bytes per attacker-declared pixel and can consume multiple gigabytes of memory. This issue is fixed in version 13.0.0.
Title Pillow: Decompression bomb check bypass in SpiderImagePlugin.seek() leads to unbounded allocation DoS
Weaknesses CWE-400
CWE-409
References
Metrics cvssV4_0

{'score': 7.1, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Oct 23, 2026, 9:18 PM
Reserved
Sep 23, 2026, 2:35 PM
Status
Analyzed
Published
Oct 21, 2026, 9:20 PM
Modified
Oct 27, 2026, 2:24 PM
Severity
Moderate
Public date
Oct 21, 2026, 9:01 PM