Vulnerability · Published Oct 20, 2026 · Assigned by curl
CVE-2026-87861cross-origin reuse of a Negotiate connection
Critical 9.1
In plain English
A critical-severity security flaw in curl from curl. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.7% (higher than 52% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS 3.1)9.1Critical
Exploit odds (30 days)0.7%top 47.6% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine:v3.23 | curl | 8.23.0-r0 | ALPINE-CVE-2026-87861 |
| Alpine:v3.24 | curl | 8.23.0-r0 | ALPINE-CVE-2026-87861 |
| Debian:14 | curl | no fix listed | DEBIAN-CVE-2026-87861 |
Affected products (as reported)
Weakness: CWE-201 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N