CVE-2024-6874: macidn punycode buffer overread

Severity: medium (CVSS 4.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.8% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2024-07-24 · updated 2026-06-17
Weakness: CWE-125

Description

libcurl's URL API function [curl_url_get()](https://curl.se/libcurl/c/curl_url_get.html) offers punycode conversions, to and from IDN. Asking to convert a name that is exactly 256 bytes, libcurl ends up reading outside of a stack based buffer when built to use the *macidn* IDN backend. The conversion function then fills up the provided buffer exactly - but does not null terminate the string. This flaw can lead to stack contents accidently getting returned as part of the converted string.

Affected products

curl: 8.8.0

References

http://www.openwall.com/lists/oss-security/2024/07/24/2
https://curl.se/docs/CVE-2024-6874.html
https://curl.se/docs/CVE-2024-6874.json
https://hackerone.com/reports/2604391
http://www.openwall.com/lists/oss-security/2024/07/24/2
https://curl.se/docs/CVE-2024-6874.html
https://curl.se/docs/CVE-2024-6874.json
https://hackerone.com/reports/2604391
https://security.netapp.com/advisory/ntap-20240822-0004/

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