VulnerabilityAnalyzed

CVE-2026-5545

MEDIUM 6.5EPSS 0.41%

Does this matter?

Lower severity and a low EPSS score (0.41%). Track it; it rarely justifies an emergency change on its own.

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...

CVSS 3.1: 6.5 MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N
EPSS: 0.41% probability · 35th percentile
CISA KEV: Not listed
Weakness: CWE-613
Affected: haxx/curl
Source: 2499f714-1537-4658-8207-48ae4bb9eae9

References

https://curl.se/docs/CVE-2026-5545.htmlPatch, Vendor Advisory
https://curl.se/docs/CVE-2026-5545.jsonVendor Advisory
https://hackerone.com/reports/3642555Exploit, Issue Tracking, Third Party Advisory
https://hackerone.com/reports/3642555Exploit, Issue Tracking, Third Party Advisory

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.