CVE-2021-25291 is a high-severity (CVSS 7.5) Out-of-bounds Read vulnerability in pillow. A fix is available for pillow — see the affected versions and patch details below.
Out of bounds read in Pillow
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2021-25291 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
pillowReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
An issue was discovered in Pillow before 8.1.1. In TiffDecode.c, there is an out-of-bounds read in TiffreadRGBATile via invalid tile boundaries.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | pillow | all versions | 8.2.0pip install --upgrade 'pillow==8.2.0' |
Affected Products
pillowpythonDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pillow, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update pillow to 8.2.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-25291 is resolved across your whole dependency graph.
Workarounds
Stop feeding it untrusted input: reject or quarantine files and payloads from unverified sources until you can upgrade, restrict accepted formats to the ones you actually need, and run the parsing or decoding step in a least-privileged sandbox or short-lived worker so a crash or corrupted read cannot reach the rest of the process.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This issue does not affect the versions of python-pillow as shipped with Red Hat Enterprise Linux 8 as it does not include the vulnerable code, which was introduced in a newer upstream version than what what shipped.
Disable the invoice generation feature to mitigate this vulnerability in Red Hat Quay.Source: Red Hat security advisory for CVE-2021-25291 (CC BY 4.0)
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Quay 3 | quay/quay-rhel8:v3.6.0-62 | RHSA-2021:3917 |
Frequently Asked Questions
Is CVE-2021-25291 in your dependencies?
Find it across PyPI, including transitive dependencies.