Reference page — cumulative record through Sunday, October 4, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2026-19931

CVE-2026-19931CRITICAL

curl curl — Negotiate ambient user conn reuse

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   N   L   N   N  U  H  H  H    9.8   .0075   53.3     —

AFFECTED
  Product  Versions                                    Fixed
  curl     7.64.1 –                                    —
  curl     6c6035532383e300c712e4c1cd9fdd749ed5cf59 –  —
  curl     8.21.0 –                                    —

TIMELINE
  Aug 15  Reserved by curl
  Sep 6   Published (CNA: curl)
  Sep 11  EXPLOIT PUBLISHED — CVE-2026-19931 (curl). Public exploit reference added.
  Sep 15  EXPLOIT PUBLISHED — CVE-2026-19931 (curl). Public exploit reference added.

CWE-488 · CNA: curl · CVSS v3.1 · 3 references · NVD status: Modified

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.

Lifecycle

Complete event history — 4 events, chronological
Date	Event	Detail
August 15, 2026	Reserved	Reserved by curl
September 6, 2026	Published	Published (CNA: curl)
September 11, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-19931 (curl). Public exploit reference added.
September 15, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-19931 (curl). Public exploit reference added.

Affected

Affected products and packages — 3 rows
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
curl	curl	—	7.64.1	—
curl	curl	—	6c6035532383e300c712e4c1cd9fdd749ed5cf59	—
curl	curl	—	8.21.0	—

Weaknesses

CWE-488

References (3)

https://curl.se/docs/CVE-2026-19931.html [Patch, Vendor Advisory]
https://curl.se/docs/CVE-2026-19931.json [Vendor Advisory]
https://hackerone.com/reports/3923520 [Exploit, Mitigation, Third Party Advisory]

Authoritative record: CVE-2026-19931 at cve.org

Vendors: curl

Weaknesses: CWE-488

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-19931 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Sunday, October 4, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.