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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.

🗓️ 03 Jul 2021 07:00:00Reported by MicrosoftType 
mscve
 mscve🔗 msrc.microsoft.com👁 2 Views

A vulnerability in urllib3 before 1.26.5 allows denial of service from URLs with many at signs in the authority.

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Detection
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Rows per page
Vulners
Node
microsoftcbl2_python-urllib3_1.25.9-3Range<1.25.9-3
OR
microsoftcm1_python-urllib3_1.25.9-2Range<1.25.9-2

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18 Feb 2026 22:13Current
9.3High risk
Vulners AI Score9.3
CVSS 25
CVSS 3.17.5
EPSS0.00863
urllib3 vulnerabilitydenial of serviceauthority componentredirects
2