NVD - CVE-2026-1965 (original) (raw)
Description
libcurl can in some circumstances reuse the wrong connection when asked to do an Negotiate-authenticated HTTP or HTTPS request. libcurl features a pool of recent connections so that subsequent requests can reuse an existing connection to avoid overhead. When reusing a connection a range of criterion must first be met. Due to a logical error in the code, a request that was issued by an application could wrongfully reuse an existing connection to the same server that was authenticated using different credentials. One underlying reason being that Negotiate sometimes authenticates *connections* and not *requests*, contrary to how HTTP is designed to work. An application that allows Negotiate authentication to a server (that responds wanting Negotiate) with `user1:password1` and then does another operation to the same server also using Negotiate but with `user2:password2` (while the previous connection is still alive) - the second request wrongly reused the same connection and since it then sees that the Negotiate negotiation is already made, it just sends the request over that connection thinking it uses the user2 credentials when it is in fact still using the connection authenticated for user1... The set of authentication methods to use is set with `CURLOPT_HTTPAUTH`. Applications can disable libcurl's reuse of connections and thus mitigate this problem, by using one of the following libcurl options to alter how connections are or are not reused: `CURLOPT_FRESH_CONNECT`, `CURLOPT_MAXCONNECTS` and `CURLMOPT_MAX_HOST_CONNECTIONS` (if using the curl_multi API).
Metrics
NVD enrichment efforts reference publicly available information to associate vector strings. CVSS information contributed by other sources is also displayed.
CVSS 4.0 Severity and Vector Strings:
NIST: NVD
NVD assessment not yet provided.
CVSS 3.x Severity and Vector Strings:
NIST: NVD
Base Score: N/A
NVD assessment not yet provided.
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
CVSS 2.0 Severity and Vector Strings:
NIST: NVD
Base Score: N/A
NVD assessment not yet provided.
References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://curl.se/docs/CVE-2026-1965.html | curl | Patch Vendor Advisory |
| https://curl.se/docs/CVE-2026-1965.json | curl | Vendor Advisory |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-305 | Authentication Bypass by Primary Weakness | CISA-ADP |
Known Affected Software Configurations Switch to CPE 2.2
Change History
3 change records found show changes
Initial Analysis by NIST 3/12/2026 10:11:19 AM
| Action | Type | Old Value | New Value |
|---|---|---|---|
| Added | CPE Configuration | OR *cpe:2.3:a:haxx:curl:*:*:*:*:*:*:*:* versions from (including) 7.10.6 up to (excluding) 8.19.0 | |
| Added | Reference Type | curl: https://curl.se/docs/CVE-2026-1965.html Types: Patch, Vendor Advisory | |
| Added | Reference Type | curl: https://curl.se/docs/CVE-2026-1965.json Types: Vendor Advisory |
CVE Modified by CISA-ADP 3/11/2026 11:16:25 AM
| Action | Type | Old Value | New Value |
|---|---|---|---|
| Added | CVSS V3.1 | AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N | |
| Added | CWE | CWE-305 |
New CVE Received from curl 3/11/2026 7:15:59 AM
| Action | Type | Old Value | New Value |
|---|---|---|---|
| Added | Description | libcurl can in some circumstances reuse the wrong connection when asked to do an Negotiate-authenticated HTTP or HTTPS request. libcurl features a pool of recent connections so that subsequent requests can reuse an existing connection to avoid overhead. When reusing a connection a range of criterion must first be met. Due to a logical error in the code, a request that was issued by an application could wrongfully reuse an existing connection to the same server that was authenticated using different credentials. One underlying reason being that Negotiate sometimes authenticates *connections* and not *requests*, contrary to how HTTP is designed to work. An application that allows Negotiate authentication to a server (that responds wanting Negotiate) with `user1:password1` and then does another operation to the same server also using Negotiate but with `user2:password2` (while the previous connection is still alive) - the second request wrongly reused the same connection and since it then sees that the Negotiate negotiation is already made, it just sends the request over that connection thinking it uses the user2 credentials when it is in fact still using the connection authenticated for user1... The set of authentication methods to use is set with `CURLOPT_HTTPAUTH`. Applications can disable libcurl's reuse of connections and thus mitigate this problem, by using one of the following libcurl options to alter how connections are or are not reused: `CURLOPT_FRESH_CONNECT`, `CURLOPT_MAXCONNECTS` and `CURLMOPT_MAX_HOST_CONNECTIONS` (if using the curl_multi API). | |
| Added | Reference | https://curl.se/docs/CVE-2026-1965.html | |
| Added | Reference | https://curl.se/docs/CVE-2026-1965.json |