PillowApplication · Python
CVE-2026-59197
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 · uneditedPillow is a Python imaging library. Prior to 12.3.0, Pillow's public rank-filter API can trigger a native heap out-of-bounds write when given a very large odd filter size because ImageFilter.RankFilter.filter() calls image.expand(size // 2, size // 2) before rank-filter size validation and ImagingExpand() computes output dimensions with unchecked signed int arithmetic. This issue is fixed in version 12.3.0.
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 confidencePillow's ImageFilter.RankFilter.filter() validates filter size AFTER calling image.expand(size // 2, size // 2), and ImagingExpand() computes output dimensions using unchecked signed int arithmetic. When a very large odd filter size is provided, integer overflow causes incorrect buffer allocation, leading to native heap out-of-bounds write.
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
< 12.3.0CVSS 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
- None
- Integrity
- Low
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/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 checksWork through these to decide whether this CVE applies to you.
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Check installed Pillow versionRun `python -c "import PIL; print(PIL.__version__)"` or `pip show pillow` to get the version numberAffected if Version is less than 12.3.0 (e.g., 12.2.0, 12.1.0, etc.)
-
Search for RankFilter usage in codeSearch source files for `from PIL import ImageFilter` and `RankFilter` imports, or search for `RankFilter(` function callsAffected if Code imports or uses ImageFilter.RankFilter
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Inspect RankFilter parametersExamine all RankFilter() calls and identify the size parameter values passed to them (e.g., RankFilter(size=31))Affected if Any RankFilter is instantiated with a very large odd number size parameter (e.g., > 1000)
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Trace user input to RankFilter sizeReview whether any user-controlled input or dynamic values are passed as the size argument to RankFilterAffected if User input can influence the filter size parameter without validation
Your environment is affected if Pillow version is below 12.3.0 AND your code uses ImageFilter.RankFilter with large odd filter sizes, especially when those sizes are derived from user input.
Generated from the published advisory. Verify against your own configuration.
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 · scoped12.3.0
Upgrade Pillow to version 12.3.0 or later. Prior to deployment, test all RankFilter usage to ensure correct behavior with the new version.
12.3.0
- Check current Pillow version using: pip show pillow or pip list | grep -i pillow
- Upgrade Pillow to version 12.3.0 or later using: pip install --upgrade 'Pillow>=12.3.0'
- Verify the upgrade was successful by running: pip show pillow and confirming the version is 12.3.0 or higher
- Test that existing code using ImageFilter.RankFilter still functions correctly after the upgrade
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
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,752.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-59197 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-59197 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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