GHSA-fc9g-5qg7-mf45 BIT-pillow-2026-112891 CVE-2026-112891

Pillow: Quadratic GIF comment copying during save

High PyPI

Severity: 0.0 / 10; High · CVSS 4.0
Exploit chance (EPSS): 0.55%; Chance of exploitation in the next 30 days. Higher than 46.00% of scored vulnerabilities.
Known exploited: No; Not in CISA's catalog
Weakness: CWE-407 Inefficient Algorithmic Complexity
Fix: 13.0.0; Upgrade pillow to this version or later

Description

On Pillow 12.3.0 and upstream main (ad277e2761b489681e71b51e91367d46b0ceabb9), a GIF with a long comment makes _get_global_header() copy portions of the comment repeatedly when saving, including comments carried over from untrusted images. I suggest provisional Moderate severity for crafted-image CPU denial of service, with CVSS-B 6.9 assuming a network service automatically opens unauthenticated uploads and they are resaved as GIFs; impact depends on input-size, concurrency, and worker CPU limits.

Affected versions

PyPI

Package	Vulnerable	Fixed in
pillow	`>= 9.2.0, < 13.0.0`	`13.0.0`

How to fix

Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.

pillow PyPI → `13.0.0`

pip

pip install --upgrade "pillow>=13.0.0"

poetry

poetry add "pillow>=13.0.0"

uv

uv add "pillow>=13.0.0"

Severity breakdown

CVSS 4.0 0.0

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

Attack vector: Network
Attack complexity: Low
Attack requirements: None
Privileges required: None
User interaction: None
Confidentiality (vulnerable system): None
Integrity (vulnerable system): None
Availability (vulnerable system): Low
Confidentiality (subsequent systems): None
Integrity (subsequent systems): None
Availability (subsequent systems): None

CVSS 3.1 7.5

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Weakness

CWE-407: Inefficient Algorithmic Complexity

An algorithm in a product has an inefficient worst-case computational complexity that may be detrimental to system performance and can be triggered by an attacker, typically using crafted manipulations that ensure that the worst case is being reached.

References

Advisories

nvd.nist.gov/vuln/detail/CVE-2026-112891

Packages

github.com/python-pillow/Pillow

Timeline

Oct 19, 2026 Published
Oct 27, 2026 Last updated by the source
Oct 31, 2026 Latest EPSS score

Advisory	Severity	Why it's related
PYSEC-2023-175 Pillow versions before v10.0.1 bundled libwebp binaries in wheels that are vulnerable to CVE-2023-5129 (previously CVE-2023-4863).	High Known exploited	Also affects pillow
GHSA-j7hp-h8jx-5ppr libwebp: OOB write in BuildHuffmanTable	High Known exploited	Also affects pillow
GHSA-78g4-xqwv-q3g8 Pillow: Bundled libopenjp2 2.5.4 in all wheels since 11.1.0 carries OSV-2025-219 heap-buffer-overflow write reachable from Image.open().load()	High	Also affects pillow
GHSA-654x-cwwv-5j9c Pillow: Arrow export leaks stale heap memory when PILLOW_ALIGNMENT > 1	Medium	Also affects pillow
GHSA-xvh5-g6gv-559v Pillow: Memory disclosure and segfault in libtiff encoder via crafted TIFF tags	High	Also affects pillow
GHSA-g7cr-3p24-7wf7 Pillow: Heap buffer overflow writing JPEG comment after ICC profile fills buffer	High	Also affects pillow
GHSA-9v9v-9qvf-h2hj Pillow: Heap over-read in WMF/EMF rendering via 16-bit dimension truncation (Windows builds)	High	Also affects pillow
GHSA-g4qv-2jxx-769h Pillow: PNG eXIf chunk makes EXIF parsing run in quadratic time	Medium	Also affects pillow

Is this in your code?

MergeHarbor checks every repository's dependencies against this database, ranks what matters by exploitability and reachability, routes it to the owning team and opens the fix pull request.

Check your repos with MergeHarbor