CVE-2026-5545— wrong 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.
libcurl是cURL开源的一个免费且易于使用的客户端 URL 传输库。 libcurl存在代码问题漏洞，该漏洞源于连接重用逻辑错误，可能导致在Negotiate认证后错误地重用使用不同凭据的现有连接。
Possible ATT&CK Techniques 1 AI
T1078 · Valid AccountsAffected Version Matrix 175
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I. Basic Information for CVE-2026-5545
Vulnerability Information
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Vulnerability Title
wrong reuse of HTTP Negotiate connection
Source: CVE Program / CVE List V5
Vulnerability Description
libcurl might in some circumstances reuse the wrong connection when asked to
do an authenticated HTTP(S) request after a Negotiate-authenticated one, when
both use the same host.
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 criteria must 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.
An application that first uses Negotiate authentication to a server with
`user1:password1` and then does another operation to the same server asking
for any authentication method but for `user2:password2` (while the previous
connection is still alive) - the second request gets confused and wrongly
reuses the same connection and sends the new request over that connection
thinking it uses a mix of user1's and user2's credentials when it is in fact
still using the connection authenticated for user1...
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
libcurl 代码问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
libcurl是cURL开源的一个免费且易于使用的客户端 URL 传输库。 libcurl存在代码问题漏洞，该漏洞源于连接重用逻辑错误，可能导致在Negotiate认证后错误地重用使用不同凭据的现有连接。
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
II. Public POCs for CVE-2026-5545
| # | POC Description | Source Link | Shenlong Link |
|---|
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Vendor Advisories for CVE-2026-5545 (2)
News Coverage for CVE-2026-5545 (1)
Same Patch Batch · curl · 2026-05-13 · 8 CVEs total
| CVE-2026-7168 | cross-proxy Digest auth state leak | |
| CVE-2026-7009 | OCSP stapling bypass with Apple SecTrust | |
| CVE-2026-6253 | proxy credentials leak over redirect-to proxy | |
| CVE-2026-6429 | netrc credential leak with reused proxy connection | |
| CVE-2026-6276 | stale custom cookie host causes cookie leak | |
| CVE-2026-4873 | connection reuse ignores TLS requirement | |
| CVE-2026-5773 | wrong reuse of SMB connection |
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V. Comments for CVE-2026-5545
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