Vulnerability · Published Sep 6, 2026 · Assigned by curl
CVE-2026-19931Negotiate ambient user conn reuse
Critical 9.8
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 55% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS 3.1)9.8Critical
Exploit odds (30 days)0.7%top 45.0% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known
Official description
A flaw in libcurl makes it wrongly reuse an HTTP connection setup for a given hostname using Negotiate authentication, when the initial request is done using empty credentials. This can make user B's request get sent over user A's previously authenticated connection.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine:v3.23 | curl | 8.22.0-r0 | ALPINE-CVE-2026-19931 |
| Alpine:v3.24 | curl | 8.22.0-r0 | ALPINE-CVE-2026-19931 |
| Debian:12 | curl | no fix listed | DEBIAN-CVE-2026-19931 |
| Debian:13 | curl | no fix listed | DEBIAN-CVE-2026-19931 |
| Debian:14 | curl | 8.22.0~rc2-1 | DEBIAN-CVE-2026-19931 |
| Ubuntu:22.04:LTS | curl | no fix listed | UBUNTU-CVE-2026-19931 |
| Ubuntu:24.04:LTS | curl | no fix listed | UBUNTU-CVE-2026-19931 |
| Ubuntu:26.04:LTS | curl | no fix listed | UBUNTU-CVE-2026-19931 |
Affected products (as reported)
Weakness: CWE-488 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H