CVE-2021-46823 — python-ldap
MEDIUMCVE-2021-46823 is a medium-severity (CVSS 6.5) CWE-1333 vulnerability in python-ldap. A fix is available for python-ldap — see the affected versions and patch details below.
Denial of Service in python-ldap
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-2021-46823 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 378,156 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
python-ldapReal-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
python-ldap before 3.4.0 is vulnerable to a denial of service when ldap.schema is used for untrusted schema definitions, because of a regular expression denial of service (ReDoS) flaw in the LDAP schema parser. By sending crafted regex input, a remote authenticated attacker could exploit this vulnerability to cause a denial of service condition.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | python-ldap | all versions | 3.4.0pip install --upgrade 'python-ldap==3.4.0' |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for python-ldap, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update python-ldap to 3.4.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-46823 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-2021-46823 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2021-46823. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
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.
Frequently Asked Questions
Is CVE-2021-46823 in your dependencies?
O3 Security finds CVE-2021-46823 across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.