---
id: CVE-2026-6276
title: |-
  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…
summary: |-
  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…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-346
  - CWE-319
vendor: haxx
product: curl
affected:
  - 'curl >= 7.71.0, < 8.20.0'
patched:
  - curl 8.20.0
published: '2026-05-13'
updated: '2026-09-15'
sourceUpdated: '2026-09-15T07:16:29.343'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-6276'
references:
  - url: 'https://curl.se/docs/CVE-2026-6276.html'
    label: 2499f714-1537-4658-8207-48ae4bb9eae9
  - url: 'https://curl.se/docs/CVE-2026-6276.json'
    label: 2499f714-1537-4658-8207-48ae4bb9eae9
  - url: 'https://hackerone.com/reports/3671818'
    label: 2499f714-1537-4658-8207-48ae4bb9eae9
  - url: 'http://www.openwall.com/lists/oss-security/2026/04/29/13'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://hackerone.com/reports/3671818'
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-6276.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-6276'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2461203'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-6276'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-6276'
  - url: 'https://access.redhat.com/errata/RHSA-2026:12916'
tags:
  - nvd
  - cve.org
  - exploit-available
  - csaf
  - vex
  - red-hat
  - score-dispute
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-05-13T17:24:29.094167Z'
epss: 0.00349
epssPercentile: 0.25749
ingestedAt: '2026-09-15T07:33:29.266Z'
scores:
  nvd: 7.5
  vendor: 3.7
---

## Overview

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.

## Affected

- `curl >= 7.71.0, < 8.20.0`

## Remediation

Upgrade past the affected range:

- `curl 8.20.0`

## Vendor advisories

- **RHSA-2026:12916** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-05-02 · [advisory](https://access.redhat.com/errata/RHSA-2026:12916)
- **Red Hat VEX** · Low · affected: Confidential Compute Attestation, Logging Subsystem for Red Hat OpenShift, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, … · no fix planned: Confidential Compute Attestation, Logging Subsystem for Red Hat OpenShift, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, … · updated 2026-09-15 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-6276.json)