CVE-2026-19931 PUBLISHED

Negotiate ambient user conn reuse

Assigner: curl
Reserved: 15.08.2026 Published: 06.09.2026 Updated: 06.09.2026

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.

Product Status

Vendor curl
Product curl
Versions Default: unaffected
  • affected from 8.21.0 to 8.21.0 (incl.)
  • affected from 8.20.0 to 8.20.0 (incl.)
  • affected from 8.19.0 to 8.19.0 (incl.)
  • affected from 8.18.0 to 8.18.0 (incl.)
  • affected from 8.17.0 to 8.17.0 (incl.)
  • affected from 8.16.0 to 8.16.0 (incl.)
  • affected from 8.15.0 to 8.15.0 (incl.)
  • affected from 8.14.1 to 8.14.1 (incl.)
  • affected from 8.14.0 to 8.14.0 (incl.)
  • affected from 8.13.0 to 8.13.0 (incl.)
  • affected from 8.12.1 to 8.12.1 (incl.)
  • affected from 8.12.0 to 8.12.0 (incl.)
  • affected from 8.11.1 to 8.11.1 (incl.)
  • affected from 8.11.0 to 8.11.0 (incl.)
  • affected from 8.10.1 to 8.10.1 (incl.)
  • affected from 8.10.0 to 8.10.0 (incl.)
  • affected from 8.9.1 to 8.9.1 (incl.)
  • affected from 8.9.0 to 8.9.0 (incl.)
  • affected from 8.8.0 to 8.8.0 (incl.)
  • affected from 8.7.1 to 8.7.1 (incl.)
  • affected from 8.7.0 to 8.7.0 (incl.)
  • affected from 8.6.0 to 8.6.0 (incl.)
  • affected from 8.5.0 to 8.5.0 (incl.)
  • affected from 8.4.0 to 8.4.0 (incl.)
  • affected from 8.3.0 to 8.3.0 (incl.)
  • affected from 8.2.1 to 8.2.1 (incl.)
  • affected from 8.2.0 to 8.2.0 (incl.)
  • affected from 8.1.2 to 8.1.2 (incl.)
  • affected from 8.1.1 to 8.1.1 (incl.)
  • affected from 8.1.0 to 8.1.0 (incl.)
  • affected from 8.0.1 to 8.0.1 (incl.)
  • affected from 8.0.0 to 8.0.0 (incl.)
  • affected from 7.88.1 to 7.88.1 (incl.)
  • affected from 7.88.0 to 7.88.0 (incl.)
  • affected from 7.87.0 to 7.87.0 (incl.)
  • affected from 7.86.0 to 7.86.0 (incl.)
  • affected from 7.85.0 to 7.85.0 (incl.)
  • affected from 7.84.0 to 7.84.0 (incl.)
  • affected from 7.83.1 to 7.83.1 (incl.)
  • affected from 7.83.0 to 7.83.0 (incl.)
  • affected from 7.82.0 to 7.82.0 (incl.)
  • affected from 7.81.0 to 7.81.0 (incl.)
  • affected from 7.80.0 to 7.80.0 (incl.)
  • affected from 7.79.1 to 7.79.1 (incl.)
  • affected from 7.79.0 to 7.79.0 (incl.)
  • affected from 7.78.0 to 7.78.0 (incl.)
  • affected from 7.77.0 to 7.77.0 (incl.)
  • affected from 7.76.1 to 7.76.1 (incl.)
  • affected from 7.76.0 to 7.76.0 (incl.)
  • affected from 7.75.0 to 7.75.0 (incl.)
  • affected from 7.74.0 to 7.74.0 (incl.)
  • affected from 7.73.0 to 7.73.0 (incl.)
  • affected from 7.72.0 to 7.72.0 (incl.)
  • affected from 7.71.1 to 7.71.1 (incl.)
  • affected from 7.71.0 to 7.71.0 (incl.)
  • affected from 7.70.0 to 7.70.0 (incl.)
  • affected from 7.69.1 to 7.69.1 (incl.)
  • affected from 7.69.0 to 7.69.0 (incl.)
  • affected from 7.68.0 to 7.68.0 (incl.)
  • affected from 7.67.0 to 7.67.0 (incl.)
  • affected from 7.66.0 to 7.66.0 (incl.)
  • affected from 7.65.3 to 7.65.3 (incl.)
  • affected from 7.65.2 to 7.65.2 (incl.)
  • affected from 7.65.1 to 7.65.1 (incl.)
  • affected from 7.65.0 to 7.65.0 (incl.)
  • affected from 7.64.1 to 7.64.1 (incl.)

Credits

  • Martin Dukek finder
  • Stefan Eissing remediation developer

References

Problem Types

  • CWE-488 Exposure of Data Element to Wrong Session