Vulnerability in Curl
CVE-2026-19931
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.007 (54.3th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 54th percentile — 54.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.012 · newest: 0.007 · change: -0.004
Affected products
Weakness classification (CWE)
References
- 2499f714-1537-4658-8207-48ae4bb9eae9 (Vendor Advisory)
- 2499f714-1537-4658-8207-48ae4bb9eae9 (Patch, Vendor Advisory)
- 2499f714-1537-4658-8207-48ae4bb9eae9 (Exploit, Third Party Advisory, Mitigation)
Frequently asked questions
- What is CVE-2026-19931?
- CVE-2026-19931 is a critical-severity vulnerability in Curl, classified under CWE-488. CVSS score: 9.8/10. Published 2026-09-06.
- How severe is CVE-2026-19931?
- Critical severity. CVSS v3 base score is 9.8 out of 10.