CVE-2026-5545
wrong reuse of HTTP Negotiate connection
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...
INFO
Published Date :
May 13, 2026, 1:01 p.m.
Last Modified :
May 13, 2026, 7:31 p.m.
Remotely Exploit :
Yes !
Source :
2499f714-1537-4658-8207-48ae4bb9eae9
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | MEDIUM | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | ||||
| CVSS 3.1 | MEDIUM | [email protected] |
Solution
- Update libcurl to the latest version.
- Review application authentication configurations.
- Test authenticated request flows thoroughly.
- Monitor connection reuse behavior.
Public PoC/Exploit Available at Github
CVE-2026-5545 has a 2 public
PoC/Exploit available at Github.
Go to the Public Exploits tab to see the list.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-5545.
| URL | Resource |
|---|---|
| https://curl.se/docs/CVE-2026-5545.html | Patch Vendor Advisory |
| https://curl.se/docs/CVE-2026-5545.json | Vendor Advisory |
| https://hackerone.com/reports/3642555 | Exploit Issue Tracking Third Party Advisory |
| https://hackerone.com/reports/3642555 | Exploit Issue Tracking Third Party Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-5545 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-5545
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
RAD Security Image Scanner
Dockerfile Makefile Go
None
Shell Python
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-5545 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-5545 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
May. 13, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N Added CWE CWE-613 Added CPE Configuration OR *cpe:2.3:a:haxx:curl:*:*:*:*:*:*:*:* versions from (including) 7.10.6 up to (excluding) 8.20.0 Added Reference Type curl: https://curl.se/docs/CVE-2026-5545.html Types: Patch, Vendor Advisory Added Reference Type curl: https://curl.se/docs/CVE-2026-5545.json Types: Vendor Advisory Added Reference Type CISA-ADP: https://hackerone.com/reports/3642555 Types: Exploit, Issue Tracking, Third Party Advisory Added Reference Type curl: https://hackerone.com/reports/3642555 Types: Exploit, Issue Tracking, Third Party Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
May. 13, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N Added Reference https://hackerone.com/reports/3642555 -
New CVE Received by 2499f714-1537-4658-8207-48ae4bb9eae9
May. 13, 2026
Action Type Old Value New Value Added 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... Added Reference https://curl.se/docs/CVE-2026-5545.html Added Reference https://curl.se/docs/CVE-2026-5545.json Added Reference https://hackerone.com/reports/3642555