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CVE-2026-1965— bad reuse of HTTP Negotiate connection

Quick assessment

Affected
curl curl
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

curl是cURL开源的一款用于从服务器传输数据或向服务器传输数据的工具。 curl存在安全漏洞，该漏洞源于逻辑错误导致连接重用不当，可能导致使用不同凭据的请求错误地重用同一连接。

AI Predicted 6.5 Difficulty: Moderate EPSS 0.26% · P16

Affected Version Matrix 174

VendorProduct Version RangeStatus
curl curl 7.10.6< 8.14.2 affected
8.15.0< 8.16.1 affected
8.17.0< 8.19.0 affected
e56ae1426cb7a0a4a427cf8d6099a821fdaae428< f1a39f221d57354990e3eeeddc3404aede2aff70 affected
8.18.0 affected
8.17.0 affected
8.16.0 affected
8.15.0 affected
… +166 more rows
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I. Basic Information for CVE-2026-1965

Vulnerability Information
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Vulnerability Title
bad reuse of HTTP Negotiate connection
Source: CVE Program / CVE List V5
Vulnerability 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 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).
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
使用基本弱点进行的认证绕过
Source: CVE Program / CVE List V5
Vulnerability Title
curl 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
curl是cURL开源的一款用于从服务器传输数据或向服务器传输数据的工具。 curl存在安全漏洞，该漏洞源于逻辑错误导致连接重用不当，可能导致使用不同凭据的请求错误地重用同一连接。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
curl curl 7.10.6 ~ 8.14.2 -
curl curl e56ae1426cb7a0a4a427cf8d6099a821fdaae428 ~ f1a39f221d57354990e3eeeddc3404aede2aff70 -
curl curl 8.18.0 -

II. Public POCs for CVE-2026-1965

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III. Intelligence Information for CVE-2026-1965

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Vendor Advisories for CVE-2026-1965 (1)

Same Patch Batch · curl · 2026-03-11 · 4 CVEs total

CVE-2026-3805 use after free in SMB connection reuse
CVE-2026-3784 wrong proxy connection reuse with credentials
CVE-2026-3783 token leak with redirect and netrc

IV. Related Vulnerabilities

Same product: curl
Same vendor: curl
Same weakness: CWE-305

V. Comments for CVE-2026-1965

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