CVE-2021-33503
Catastrophic backtracking in URL authority parser when passed URL containing many @ characters
7.5
HIGH
CVSS 3.1
EPSS 0.86%
Description
An issue was discovered in urllib3 before 1.26.5. When provided with a URL containing many @ characters in the authority component, the authority regular expression exhibits catastrophic backtracking, causing a denial of service if a URL were passed as a parameter or redirected to via an HTTP redirect.
How to fix CVE-2021-33503
To remediate CVE-2021-33503, upgrade the affected package to a fixed version below.
- —upgrade to 1.26.5-1~exp1 or later
- —upgrade to 1.26.5 or later
- —upgrade to 2d4a3fee6de2fa45eb82169361918f759269b4ec or later
Is CVE-2021-33503 being exploited?
Low — EPSS is 0.9%, meaning exploitation activity has not been observed at scale.
Affected packages (3)
- from 0, < 1.26.5-1~exp1
- >= 1.25.4, < 1.26.5
- from 0, < 2d4a3fee6de2fa45eb82169361918f759269b4ec | from 0, < 1.26.5
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 4.0 | — | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N |
| osv | CVSS 3.1 | HIGH7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |