CVE-2021-4287 is a medium-severity (CVSS 6.5) CWE-61 vulnerability in binwalk. A fix is available for binwalk — see the affected versions and patch details below.
binwalk vulnerable to UNIX Symbolic Link (Symlink) Following
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2021-4287.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2021-4287 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,567 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
binwalkReal-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
A vulnerability, which was classified as problematic, was found in ReFirm Labs binwalk up to 2.3.2. Affected is an unknown function of the file src/binwalk/modules/extractor.py of the component Archive Extraction Handler. The manipulation leads to symlink following. It is possible to launch the attack remotely. Upgrading to version 2.3.3 is able to address this issue. The name of the patch is fa0c0bd59b8588814756942fe4cb5452e76c1dcd. It is recommended to upgrade the affected component. The identifier of this vulnerability is VDB-216876.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | binwalk | all versions | 2.3.3pip install --upgrade 'binwalk==2.3.3' |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for binwalk, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update binwalk to 2.3.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-4287 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2021-4287 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2021-4287. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2021-4287 in your dependencies?
O3 Security finds CVE-2021-4287 across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.