CVE-2026-40192: Pillow FITS GZIP Decompression Bomb Vulnerability

HIGH
Advisory Identifier: GHSA-whj4-6x5x-4v2j
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CVSS 7.5
CWE-400 CWE-770
Published
Advisory Summary

CVE-2026-40192 is a HIGH (CVSS 7.5) fits gzip decompression bomb vulnerability (CWE-400: Uncontrolled Resource Consumption) affecting Pillow libraries in the PyPI ecosystem. The issue involves fits gzip decompression bomb in pillow. Remediation is available by upgrading affected packages to version 12.2.0.

CVE-2026-40192 at a Glance

CVE Identifier CVE-2026-40192
GHSA Identifier GHSA-whj4-6x5x-4v2j
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-400: Uncontrolled Resource Consumption
Affected Product Pillow
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 7.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability High (A:H)

How to Fix CVE-2026-40192

To remediate this vulnerability, upgrade all affected Pillow dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

pillow fixed: 12.2.0 
pip install pillow>=12.2.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show pillow

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-40192, inspect your installed packages using pip:

pip show pillow

Analyze the terminal output to locate any version of Pillow in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 12.2.0), your application is affected.

Note: The pip show pillow command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-400: Uncontrolled Resource Consumption, where the product does not properly control the allocation and maintenance of a limited resource. In Pillow, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Impact Pillow did not limit the amount of GZIP-compressed data read when decoding a FITS image, making it vulnerable to decompression bomb attacks. A specially crafted FITS file could cause unbounded memory consumption, leading to denial of service (OOM crash or severe performance degradation). ### Patches The amount of data read is now limited to the necessary amount. Fixed in Pillow 12.2.0 (PR #9521). ### Workarounds Avoid Pillow >= 10.3.0, < 12.2.0 Only open [specific image formats](https://pillow.readthedocs.io/en/stable/releasenotes/8.0.0.html#image-open-add-formats-parameter), excluding FITS.

CVE-2026-40192 Affected Pillow Versions

1 component(s)
Fixed Versions:
12.2.0
Product / Package Ecosystem Affected Versions Fixed Version
pillow
pypi/pillow
PyPI
≥ 10.3.0
< 12.2.0
12.2.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/python-pillow/Pillow/security/advisories/GHSA-whj4-6x5x-4v2j
NVD — CVE-2026-40192 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-40192
Pillow Source Repository REPOSITORY
https://github.com/python-pillow/Pillow/pull/9521
Security Fix Commit FIX COMMIT
https://github.com/python-pillow/Pillow/commit/3cb854e8b2bab43f40e342e665f9340d861aa628
Pillow Source Repository REPOSITORY
https://github.com/python-pillow/Pillow
Pillow Release RELEASE
https://pillow.readthedocs.io/en/stable/releasenotes/12.2.0.html#prevent-fits-decompression-bomb

Frequently Asked Questions

What is CVE-2026-40192?
CVE-2026-40192 is a security vulnerability in Pillow involving FITS GZIP decompression bomb in Pillow under CWE-400: Uncontrolled Resource Consumption.
Which Pillow versions are affected?
Affected versions include releases prior to 12.2.0 across affected packages: pillow.
What version fixes CVE-2026-40192?
Upgrading to 12.2.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is pillow affected?
Yes, pillow is affected in releases prior to 12.2.0. Upgrade your dependency to 12.2.0 or later.
What is the CVSS score of CVE-2026-40192?
CVE-2026-40192 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2026-40192?
CVE-2026-40192 is classified under CWE-400: Uncontrolled Resource Consumption (The product does not properly control the allocation and maintenance of a limited resource.).
How can I check PyPI dependencies for CVE-2026-40192?
Run the dependency tree command: 'pip show pillow'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-whj4-6x5x-4v2j",
  "modified" : "2026-04-27T16:21:39Z",
  "published" : "2026-04-13T19:22:35Z",
  "aliases" : [ "CVE-2026-40192" ],
  "summary" : "FITS GZIP decompression bomb in Pillow",
  "details" : "### Impact\nPillow did not limit the amount of GZIP-compressed data read when decoding a FITS image, making it vulnerable to decompression bomb attacks. A specially crafted FITS file could cause unbounded memory consumption, leading to denial of service (OOM crash or severe performance degradation).\n\n### Patches\nThe amount of data read is now limited to the necessary amount.\nFixed in Pillow 12.2.0 (PR #9521).\n\n### Workarounds\nAvoid Pillow >= 10.3.0, < 12.2.0\nOnly open [specific image formats](https://pillow.readthedocs.io/en/stable/releasenotes/8.0.0.html#image-open-add-formats-parameter), excluding FITS.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "pillow"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "10.3.0"
      }, {
        "fixed" : "12.2.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/python-pillow/Pillow/security/advisories/GHSA-whj4-6x5x-4v2j"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-40192"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/python-pillow/Pillow/pull/9521"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/python-pillow/Pillow/commit/3cb854e8b2bab43f40e342e665f9340d861aa628"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/python-pillow/Pillow"
  }, {
    "type" : "WEB",
    "url" : "https://pillow.readthedocs.io/en/stable/releasenotes/12.2.0.html#prevent-fits-decompression-bomb"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-400", "CWE-770" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-13T19:22:35Z",
    "nvd_published_at" : "2026-04-15T23:16:10Z"
  }
}