CVE-2021-25289: Pillow Out Of Bounds Write Vulnerability

CRITICAL
Advisory Identifier: GHSA-57h3-9rgr-c24m
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CVSS 9.8
CWE-787
Published
Advisory Summary

CVE-2021-25289 is a CRITICAL (CVSS 9.8) out of bounds write vulnerability (CWE-787: Out-of-bounds Write) affecting Pillow libraries in the PyPI ecosystem. The issue involves out of bounds write in pillow. Remediation is available by upgrading affected packages to version 8.1.1.

CVE-2021-25289 at a Glance

CVE Identifier CVE-2021-25289
GHSA Identifier GHSA-57h3-9rgr-c24m
Severity CRITICAL
CVSS v3.1 Base Score 9.8
CWE Classification CWE-787: Out-of-bounds Write
Affected Product Pillow
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 9.8

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:H/I:H/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 High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2021-25289

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: 8.1.1 
pip install pillow>=8.1.1
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-2021-25289, 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 8.1.1), 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-787: Out-of-bounds Write, where the product writes data past the end, or before the beginning, of the intended buffer. 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

An issue was discovered in Pillow before 8.1.1. TiffDecode has a heap-based buffer overflow when decoding crafted YCbCr files because of certain interpretation conflicts with LibTIFF in RGBA mode. NOTE: this issue exists because of an incomplete fix for CVE-2020-35654.

CVE-2021-25289 Affected Pillow Versions

1 component(s)
Fixed Versions:
8.1.1
Product / Package Ecosystem Affected Versions Fixed Version
pillow
pypi/pillow
PyPI
< 8.1.1
8.1.1

References

NVD — CVE-2021-25289 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-25289
Security Fix Commit FIX COMMIT
https://github.com/python-pillow/Pillow/commit/3fee28eb9479bf7d59e0fa08068f9cc4a6e2f04c
Security Fix Commit FIX COMMIT
https://github.com/python-pillow/Pillow/commit/cbfdde7b1f2295059a20a539ee9960f0bec7b299
GitHub Advisory / Wiki ADVISORY
https://github.com/advisories/GHSA-57h3-9rgr-c24m
Pillow Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/pillow/PYSEC-2021-35.yaml
Pillow Source Repository REPOSITORY
https://github.com/python-pillow/Pillow
Pillow Release RELEASE
https://pillow.readthedocs.io/en/stable/releasenotes/8.1.1.html
Pillow Security Information SECURITY
https://security.gentoo.org/glsa/202107-33

Frequently Asked Questions

What is CVE-2021-25289?
CVE-2021-25289 is a security vulnerability in Pillow involving Out of bounds write in Pillow under CWE-787: Out-of-bounds Write.
Which Pillow versions are affected?
Affected versions include releases prior to 8.1.1 across affected packages: pillow.
What version fixes CVE-2021-25289?
Upgrading to 8.1.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is pillow affected?
Yes, pillow is affected in releases prior to 8.1.1. Upgrade your dependency to 8.1.1 or later.
What is the CVSS score of CVE-2021-25289?
CVE-2021-25289 has a CVSS v3.1 base score of 9.8 (CRITICAL) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2021-25289?
CVE-2021-25289 is classified under CWE-787: Out-of-bounds Write (The product writes data past the end, or before the beginning, of the intended buffer.).
How can I check PyPI dependencies for CVE-2021-25289?
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-57h3-9rgr-c24m",
  "modified" : "2024-10-08T13:11:32Z",
  "published" : "2021-03-29T16:35:16Z",
  "aliases" : [ "CVE-2021-25289" ],
  "summary" : "Out of bounds write in Pillow",
  "details" : "An issue was discovered in Pillow before 8.1.1. TiffDecode has a heap-based buffer overflow when decoding crafted YCbCr files because of certain interpretation conflicts with LibTIFF in RGBA mode. NOTE: this issue exists because of an incomplete fix for CVE-2020-35654.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "pillow"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "8.1.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-25289"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/python-pillow/Pillow/commit/3fee28eb9479bf7d59e0fa08068f9cc4a6e2f04c"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/python-pillow/Pillow/commit/cbfdde7b1f2295059a20a539ee9960f0bec7b299"
  }, {
    "type" : "ADVISORY",
    "url" : "https://github.com/advisories/GHSA-57h3-9rgr-c24m"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/pillow/PYSEC-2021-35.yaml"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/python-pillow/Pillow"
  }, {
    "type" : "WEB",
    "url" : "https://pillow.readthedocs.io/en/stable/releasenotes/8.1.1.html"
  }, {
    "type" : "WEB",
    "url" : "https://security.gentoo.org/glsa/202107-33"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-787" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-03-22T22:07:48Z",
    "nvd_published_at" : "2021-03-19T04:15:00Z"
  }
}