PillowApplication · Python
CVE-2021-27922
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 before 8.1.2 allows attackers to cause a denial of service (memory consumption) because the reported size of a contained image is not properly checked for an ICNS container, and thus an attempted memory allocation can be very large.
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 · moderate confidencePillow before 8.1.2 fails to properly validate the reported size of images embedded in ICNS container files before attempting memory allocation. An attacker can craft or provide a malicious ICNS file with an exaggerated reported image size, causing the library to attempt allocating an extremely large memory buffer, leading to memory exhaustion and denial of service.
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
< 8.1.1
FedoraOperating system
= 32= 33= 34CVSS 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
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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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Determine installed Pillow versionRun 'pip show pillow' or 'python -c "import PIL; print(PIL.__version__)"' to retrieve the installed Pillow version numberAffected if The version is less than 8.1.1
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Confirm ICNS support in PillowCheck if Pillow was built with ICNS decoder support by running 'python -c "from PIL import Image; print(Image.open('test.icns'))' with a valid ICNS file, or inspect installed decoders via 'python -c "from PIL import features; print(features.check('icns'))'"Affected if ICNS decoding is available and enabled in the Pillow installation
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Identify ICNS file processing in your applicationSearch application code, scripts, or automated pipelines for references to '.icns' file extensions or ICNS-related Pillow functions such as 'Image.open()' handling ICNS filesAffected if Your code or automated processes accept and process ICNS files from any source
You are affected if Pillow version is below 8.1.1 AND your environment processes ICNS image files, as the memory exhaustion flaw can be triggered by a malicious ICNS file with an exaggerated reported image size.
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.
From vendor data8.1.1
Upgrade Pillow to version 8.1.2 or later. If upgrading is not immediately possible, limit or restrict ICNS file processing from untrusted sources to mitigate memory exhaustion risks.
Fix this in Pillow
Scoped from the published advisory
- Consultation2.0 h
- Implementation1.0 h
- Testing3.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,936.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-27922 — 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-2021-27922 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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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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