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[ADVISORY] curl CVE-2025-14017: broken TLS options for threaded LDAPS
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From: Daniel Stenberg via curl-library <curl-library_at_lists.haxx.se>
Date: Wed, 7 Jan 2026 08:09:18 +0100 (CET)
broken TLS options for threaded LDAPS
=====================================
Project curl Security Advisory, January 7 2026 -
[Permalink](https://curl.se/docs/CVE-2025-14017.html)
VULNERABILITY
-------------
When doing multithreaded LDAPS transfers (LDAP over TLS) with libcurl,
changing TLS options in one thread would inadvertently change them globally
and therefore possibly also affect other concurrently setup transfers.
Disabling certificate verification for a specific transfer could
unintentionally disable the feature for other threads as well.
INFO
Date: Wed, 7 Jan 2026 08:09:18 +0100 (CET)
broken TLS options for threaded LDAPS
=====================================
Project curl Security Advisory, January 7 2026 -
[Permalink](https://curl.se/docs/CVE-2025-14017.html)
VULNERABILITY
-------------
When doing multithreaded LDAPS transfers (LDAP over TLS) with libcurl,
changing TLS options in one thread would inadvertently change them globally
and therefore possibly also affect other concurrently setup transfers.
Disabling certificate verification for a specific transfer could
unintentionally disable the feature for other threads as well.
INFO
---- curl contains support for several different LDAP backends. This flaw only exists when libcurl was built to use the "legacy" non-Windows LDAP support (the `lib/ldap.c` source code). Notably, builds using OpenLDAP are not affected. It does not apply to users of WinLDAP (the flavor of LDAP provided in Windows) since that API does not offer those TLS related options. This is only a potential problem when doing LDAP transfers concurrently in more than one thread. The global state was used for the connection setup (only), so this vulnerability is highly timing sensitive. The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2025-14017 to this issue. CWE-567: Unsynchronized Access to Shared Data in a Multithreaded Context Severity: Medium AFFECTED VERSIONS ----------------- - Affected versions: curl 7.17.0 to and including 8.17.0 - Not affected versions: curl < 7.17.0 and >= 8.18.0 - Introduced-in: https://github.com/curl/curl/commit/ccba0d10b6baf5c73ca libcurl is used by many applications, but not always advertised as such! This bug is not considered a *C mistake*. It is not likely to have been avoided had we not been using C. This flaw **does not** affect the curl command line tool. SOLUTION ------------ Starting in curl 8.18.0, this mistake is fixed. - Fixed-in: https://github.com/curl/curl/commit/39d1976b7f709a516e324333 RECOMMENDATIONS -------------- A - Upgrade curl to version 8.18.0 B - Build curl with OpenLDAP C - Avoid using LDAP TIMELINE -------- This issue was reported to the curl project on December 1, 2025. curl 8.18.0 was released on January 7 2026 around 07:00 UTC, coordinated with the publication of this advisory. The curl security team is not aware of any active exploits using this vulnerability. CREDITS ------- - Reported-by: Stanislav Fort (Aisle Research) - Patched-by: Daniel Stenberg Thanks a lot! -- / daniel.haxx.se || https://rock-solid.curl.dev -- Unsubscribe: https://lists.haxx.se/mailman/listinfo/curl-library Etiquette: https://curl.se/mail/etiquette.htmlReceived on 2026-01-07