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...
Metrics
Affected Vendors & Products
| Vendors | Products |
|---|---|
| Curl |
|
No data.
No data.
References
History
Wed, 13 May 2026 09:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | A flaw was found in libcurl. An application using libcurl that performs an authenticated HTTP(S) request after a Negotiate-authenticated one to the same host may incorrectly reuse the previous connection. This authentication bypass vulnerability allows the second request to be sent over a connection authenticated with different credentials, potentially leading to unauthorized access or information disclosure. | 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... |
| Title | curl: libcurl: Authentication bypass due to incorrect HTTP Negotiate connection reuse | wrong reuse of HTTP Negotiate connection |
| References |
|
Fri, 01 May 2026 01:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| First Time appeared |
Curl
Curl libcurl |
|
| Vendors & Products |
Curl
Curl libcurl |
Fri, 01 May 2026 00:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | A flaw was found in libcurl. An application using libcurl that performs an authenticated HTTP(S) request after a Negotiate-authenticated one to the same host may incorrectly reuse the previous connection. This authentication bypass vulnerability allows the second request to be sent over a connection authenticated with different credentials, potentially leading to unauthorized access or information disclosure. | |
| Title | curl: libcurl: Authentication bypass due to incorrect HTTP Negotiate connection reuse | |
| Weaknesses | CWE-488 | |
| References |
| |
| Metrics |
threat_severity
|
cvssV3_1
|
MITRE
Status: PUBLISHED
Assigner: curl
Published:
Updated: 2026-05-13T08:27:26.065Z
Reserved: 2026-04-04T12:10:07.125Z
Link: CVE-2026-5545
Vulnrichment
No data.
NVD
No data.
Redhat