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CVE-2026-19931

Negotiate ambient user conn reuse

Critical9.8Public exploitEPSS 0.75%
Published
Updated
Reserved
Assigned by
curl

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.

Public exploit

A reference of the record is tagged as an exploit or proof of concept: anyone can try it against an unpatched system. CISA's SSVC rates its exploitation: a proof of concept is public.

Timeline

  1. ID reserved

    By curl

  2. · 22 days later

    Published

  3. · 9 days later

    Record updated

Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.

Scores

CVSS scores of CVE-2026-19931, by who scored it
Scored byCVSSScoreVector
CISA-ADPADP (enrichment)3.1Critical9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVDNVD · Modified3.1Critical9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS (exploitation in 30 days)
0.75% · top 45% of all CVEs (7 Nov 2026)
CISA SSVC
Exploitation: poc · Automatable: yes · Technical impact: total
Loading the EPSS history…

The list uses the assigner's score when there is one, then CISA's, then NVD's: Critical 9.8.

Weakness

Affected products

  • curl · curl

    • affected 7.64.1 – < 8.14.2
    • affected 8.15.0 – < 8.16.1
    • affected 8.17.0 – < 8.20.1
    • affected 8.21.0 – < 8.22.0

  • curl · curl

    • affected 6c6035532383e300c712e4c1cd9fdd749ed5cf59 – < 7103a93b05bc69ea98ed9d05d02fa9eeba533f2f

  • curl · curl

    • affected 8.21.0
    • affected 8.20.0
    • affected 8.19.0
    • affected 8.18.0
    • affected 8.17.0
    • affected 8.16.0
    • affected 8.15.0
    • affected 8.14.1
    • affected 8.14.0
    • affected 8.13.0
    • affected 8.12.1
    • affected 8.12.0
    • affected 8.11.1
    • affected 8.11.0
    • affected 8.10.1
    • affected 8.10.0
    • affected 8.9.1
    • affected 8.9.0
    • affected 8.8.0
    • affected 8.7.1
    • affected 8.7.0
    • affected 8.6.0
    • affected 8.5.0
    • affected 8.4.0
    • affected 8.3.0
    • affected 8.2.1
    • affected 8.2.0
    • affected 8.1.2
    • affected 8.1.1
    • affected 8.1.0
    • affected 8.0.1
    • affected 8.0.0
    • affected 7.88.1
    • affected 7.88.0
    • affected 7.87.0
    • affected 7.86.0
    • affected 7.85.0
    • affected 7.84.0
    • affected 7.83.1
    • affected 7.83.0
    • and 26 more

References (3)

Sources

The same CVE in the primary databases and aggregators, to check against.

Badge for a README or a ticket

CVE-2026-19931 badge
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Record last updated .