Unscored severity · published Oct 20, 2026
CVE-2026-87861
cross-origin reuse of a Negotiate connection
–
CVSS
0.3%
EPSS
No
On KEV
Description
When using ambient user credentials, an HTTP request directed to one origin
may be dispatched over a connection previously authenticated via Negotiate for
a different origin, leaving the request's intended credentials unused.
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 18% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
CU
curl · curl
8.22.0 through 8.22.0; 8.21.0 through 8.21.0 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-87861
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-87861
curl.se
https://curl.se/docs/CVE-2026-87861.html
curl.se
https://curl.se/docs/CVE-2026-87861.json
hackerone.com
https://hackerone.com/reports/3972094
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