dbcve.org
PillowApplication · Python

CVE-2021-25289

CRITICAL · 9.8 CVSS v3.1 Published 2021-03-19
Fix available
A fix is available. Upgrade to 8.1.1 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Heap-based buffer overflow in Pillow's TiffDecode function when processing crafted YCbCr TIFF files. The vulnerability stems from interpretation conflicts between Pillow's handling and LibTIFF when operating in RGBA mode, causing memory corruption during image decoding.

MitigationUpgrade Pillow to version 8.1.1 or later to address the incomplete fix from CVE-2020-35654.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
PillowApplication
Affected:< 8.1.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check installed Pillow version
    Run `python -c 'import PIL; print(PIL.__version__)'` or `pip show pillow` to retrieve the installed Pillow version number
    Affected if The version is lower than 8.1.1 (e.g., 8.1.0, 8.0.0, 7.x.x, etc.)
  2. Identify TIFF processing functionality
    Search codebase or application for imports of PIL.Image, PIL.TiffImagePlugin, or any usage of Image.open() with .tif/.tiff files. Check for tiff-related processing libraries or dependencies
    Affected if The environment processes TIFF files using Pillow's TiffDecode functionality
  3. Verify YCbCr color space handling
    Inspect any TIFF image loading code to determine if the YCbCr color space is explicitly handled or if images are decoded in RGBA mode. Check for patterns like Image.open().convert('RGBA') on TIFF files or libtiff-related configurations
    Affected if YCbCr TIFF images are decoded or converted to RGBA mode in the application
  4. Check for libTIFF interaction
    Examine if the system uses libTIFF (via Pillow's Image.core interface or tiff_lzw_decoder) for TIFF decoding. Review any tiff-related configuration files or environment variables affecting TIFF handling
    Affected if Pillow's libTIFF integration is enabled and used for TIFF file processing

A user is affected if Pillow version is below 8.1.1 AND the environment processes YCbCr TIFF files, particularly when those files are decoded in RGBA mode through Pillow's TiffDecode function.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 8.1.1 or later
Fixed in 8.1.1
Interim mitigation

Upgrade Pillow to version 8.1.1 or later to address the incomplete fix from CVE-2020-35654.

Recommended fix High confidence

Pillow 8.1.1

  1. Upgrade Pillow to version 8.1.1 or later using your package manager (e.g., pip install --upgrade Pillow>=8.1.1)
  2. Verify the upgrade was successful by running 'pip show Pillow' and confirming the version number
  3. Test your application to ensure the upgrade does not break existing functionality
  4. If using a dependency manager (poetry, pipenv, conda), update the Pillow version constraint in your project files
Caveat Point releases typically have minimal breaking changes, but test thoroughly before deploying to production

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Pillow Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing8.0 h
  • Review / QA4.0 h
16.0 hours of engineering $2,680
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,288.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-25289 in production — separate from our analysis above.

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What this is

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What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data