CVE•Published 2021-05-06•Modified 2026-10-08•1 article on news•6 live references•NVD data
CVE-2021-29921Python · Python
Vulnerability data via NVD (ingested)
CVSS v3.1
9.8
CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS percentile
94
Exploit Prediction Scoring System · top 6% of all CVEs
Description
In Python before 3,9,5, the ipaddress library mishandles leading zero characters in the octets of an IP address string. This (in some situations) allows attackers to bypass access control that is based on IP addresses.
Timeline
Published 2021-05-06
Modified 2026-10-08
External references
Search for exposed instances
Shodan + Censys queries derived from NVD's CPE data. The vuln tag catches assets Shodan has explicitly linked to this CVE; the product / banner fingerprints find exposed instances even when the vuln tag was never applied (which is common).
Shodan · vuln tag21,167 hosts
vuln:CVE-2021-29921Hosts Shodan has explicitly fingerprinted as vulnerable.
Shodan · product
product:"Python Python"All exposed Python Python instances — cross-reference with the CVE's affected-version range.
Shodan · banner/body mention
http.html:"Python"HTTP body or banner mentions "Python" — catches deploys Shodan didn't identify as a product.
More intel sources (5)
Shodan report
vuln:CVE-2021-29921Country / ASN / product breakdown for the vuln query.
Censys
vulnerabilities.cve_id: CVE-2021-29921Censys host search filtered to this CVE id.
grep.app
CVE-2021-29921Public source-code mentions — fast PoC discovery.
GitHub code
CVE-2021-29921GitHub code search for direct mentions.
Google dork
"CVE-2021-29921" exploit -site:nvd.nist.govWrite-ups and news, NVD excluded.