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Vulnerability record · CVE-2023-27535 · published 30 March 2023

CVE-2023-27535: Haxx libcurl improper authentication vulnerability

Haxx · Libcurl

An authentication bypass vulnerability exists in libcurl <8.0.0 in the FTP connection reuse feature that can result in wrong credentials being used during subsequent transfers. Previously created connections are kept in a connection pool for reuse if they match the current setup. However, certain FTP settings such as CURLOPT_FTP_ACCOUNT, CURLOPT_FTP_ALTERNATIVE_TO_USER, CURLOPT_FTP_SSL_CCC, and CURLOPT_USE_SSL were not included in the configuration match checks, causing them to match too easily. This could lead to libcurl using the wrong credentials when performing a transfer, potentially allowing unauthorized access to sensitive information.

5.9 CVSS 3.1 Medium EPSS 1.6% · top 25.1% CWE-305 · CWE-305CWE-287 · Improper authentication
5.9CVSS 3.1 base score
1.6%EPSS exploitation probability, 30 days
NoNot in CISA KEV
10Affected product versions listed by NVD
10References, 2 tagged exploit
17 Jun 2026Last modified by NVD

Description

An authentication bypass vulnerability exists in libcurl <8.0.0 in the FTP connection reuse feature that can result in wrong credentials being used during subsequent transfers. Previously created connections are kept in a connection pool for reuse if they match the current setup. However, certain FTP settings such as CURLOPT_FTP_ACCOUNT, CURLOPT_FTP_ALTERNATIVE_TO_USER, CURLOPT_FTP_SSL_CCC, and CURLOPT_USE_SSL were not included in the configuration match checks, causing them to match too easily. This could lead to libcurl using the wrong credentials when performing a transfer, potentially allowing unauthorized access to sensitive information.

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

Affected products

10 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://hackerone.com/reports/1892780 ExploitThird Party Advisory
https://lists.debian.org/debian-lts-announce/2023/04/msg00025.html Mailing ListThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/36NBD5YLJXXEDZLDGNFCERW Mailing ListThird Party Advisory
https://security.gentoo.org/glsa/202310-12 Third Party Advisory
https://security.netapp.com/advisory/ntap-20230420-0010/ Third Party Advisory
https://hackerone.com/reports/1892780 ExploitThird Party Advisory
https://lists.debian.org/debian-lts-announce/2023/04/msg00025.html Mailing ListThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/36NBD5YLJXXEDZLDGNFCERW Mailing ListThird Party Advisory
https://security.gentoo.org/glsa/202310-12 Third Party Advisory
https://security.netapp.com/advisory/ntap-20230420-0010/ Third Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2023-27535), CISA KEV, FIRST EPSS (scores of 2026-09-29). This page is refreshed as NVD updates the record.