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-2026-6276

CVE-2026-6276HIGH

curl curl — stale custom cookie host causes cookie leak

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   N   L   N   N  U  N  N  H    7.5   .0035   26.2     —

AFFECTED
  Product  Versions                                    Fixed
  curl     7.71.0 –                                    —
  curl     e15e51384a423be31318b3c9c7d612a1aae661fd –  —
  curl     8.19.0 –                                    —

TIMELINE
  Apr 14  Reserved by curl
  May 13  Published (CNA: curl)
  Sep 15  EXPLOIT PUBLISHED — CVE-2026-6276 (curl). Public exploit reference added.

CWE-319, CWE-346 · CNA: curl · CVSS v3.1 · 4 references · NVD status: Modified

Description

Using libcurl, when a custom `Host:` header is first set for an HTTP request and a second request is subsequently done using the same *easy handle* but without the custom `Host:` header set, the second request would use stale information and pass on cookies meant for the first host in the second request. Leak them.

Lifecycle

Complete event history — 3 events, chronological
Date	Event	Detail
April 14, 2026	Reserved	Reserved by curl
May 13, 2026	Published	Published (CNA: curl)
September 15, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-6276 (curl). Public exploit reference added.

Affected

Affected products and packages — 3 rows
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
curl	curl	—	7.71.0	—
curl	curl	—	e15e51384a423be31318b3c9c7d612a1aae661fd	—
curl	curl	—	8.19.0	—

Weaknesses

CWE-319 · CWE-346

References (4)

http://www.openwall.com/lists/oss-security/2026/04/29/13 [Mailing List, Third Party Advisory]
https://curl.se/docs/CVE-2026-6276.html [Patch, Vendor Advisory]
https://curl.se/docs/CVE-2026-6276.json [Product]
https://hackerone.com/reports/3671818 [Exploit, Issue Tracking, Third Party Advisory]

Authoritative record: CVE-2026-6276 at cve.org

Vendors: curl

Weaknesses: CWE-319 · CWE-346

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-6276 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.