CVE-2021-29921

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.

CVSS v3.1

9.8 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v2.0

7.5 HIGHAV:N/AC:L/Au:N/C:P/I:P/A:P

EPSS

6.88% chance of exploitation in the next 30 days, 94th percentile

Published

2021-05-06

Updated

2025-11-03

Proof-of-concept exploits (2)

• sickcodes/security/blob/master/advisories/SICK-2021-014.md
• https://sick.codes/sick-2021-014

References

• CVE Record
• NVD entry

Related

• CVE-2020-25507
• CVE-2020-27402
• CVE-2020-27403
• CVE-2021-28918
• CVE-2021-29662
• CVE-2021-29922