CVE-2022-43551
Plain English Summary
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An attacker can trick curl into using an insecure HTTP connection instead of the intended secure HTTPS by manipulating the URL with special characters that confuse the software's security checks. This vulnerability occurs when the URL contains IDN characters that are converted to ASCII, allowing the attacker to bypass the HSTS protection that should enforce secure connections.
Technical Description
A vulnerability exists in curl <7.87.0 HSTS check that could be bypassed to trick it to keep using HTTP. Using its HSTS support, curl can be instructed to use HTTPS instead of using an insecure clear-text HTTP step even when HTTP is provided in the URL. However, the HSTS mechanism could be bypassed if the host name in the given URL first uses IDN characters that get replaced to ASCII counterparts as part of the IDN conversion. Like using the character UTF-8 U+3002 (IDEOGRAPHIC FULL STOP) instead of the common ASCII full stop (U+002E) `.`. Then in a subsequent request, it does not detect the HSTS state and makes a clear text transfer. Because it would store the info IDN encoded but look for it IDN decoded.
CVSS Vector Analysis
Vector String
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:NExploit Resources
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Official References
Quick Information
Published
Dec 23, 2022
about 3 years ago
Last Modified
Feb 13, 2026
7 days ago
Vendor
haxx
Product
curl
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This vulnerability allows an attacker to manipulate data sent in a POST request by exploiting a flaw in how the curl library handles reused connections, potentially leading to the wrong data being sent or causing the application to crash. It occurs when a connection that was previously used for a PUT request is reused for a POST request without properly resetting the data handling, which could happen in applications that frequently switch between these types of requests.
This vulnerability allows an attacker to trick curl into using an insecure HTTP connection instead of the intended secure HTTPS connection by manipulating the URL with special characters. This can happen when the URL includes international domain names that get converted to ASCII, making it possible for the attacker to bypass security checks designed to enforce HTTPS.