CVE-2026-1965bad reuse of HTTP Negotiate connection
- 6.5MediumCVSS base score
- 0.30%Exploitation in 30 daysEPSS · top 77% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
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).
Timeline
ID reserved
By curl
- 34 days later
· 34 days later
Published
- 6 months later
· 6 months later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| CISA-ADPADP (enrichment) | 3.1 | Medium6.5 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N |
| NVDNVD · Modified | 3.1 | Medium6.5 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N |
- EPSS (exploitation in 30 days)
- 0.30% · top 77% of all CVEs (13 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.5.
Affected products
- affected 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 8.14.1
- affected 8.14.0
- affected 8.13.0
- affected 8.12.1
- affected 8.12.0
- affected 8.11.1
- affected 8.11.0
- affected 8.10.1
- affected 8.10.0
- affected 8.9.1
- affected 8.9.0
- affected 8.8.0
- affected 8.7.1
- affected 8.7.0
- affected 8.6.0
- affected 8.5.0
- affected 8.4.0
- affected 8.3.0
- affected 8.2.1
- affected 8.2.0
- affected 8.1.2
- affected 8.1.1
- affected 8.1.0
- affected 8.0.1
- affected 8.0.0
- affected 7.88.1
- affected 7.88.0
- affected 7.87.0
- affected 7.86.0
- affected 7.85.0
- affected 7.84.0
- affected 7.83.1
- affected 7.83.0
- affected 7.82.0
- affected 7.81.0
- affected 7.80.0
- and 130 more
References
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-11135 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-1965)Record last updated .