---
id: CVE-2026-11856
title: |-
  Successfully using libcurl to do a transfer to a specific HTTP origin
  (`hostA`) with **Digest** authentication and then changing the origin to a
  different one (`hostB`) for a second transfer, reusing the same handle, makes
  libcurl wrongl…
summary: |-
  Successfully using libcurl to do a transfer to a specific HTTP origin
  (`hostA`) with **Digest** authentication and then changing the origin to a
  different one (`hostB`) for a second transfer, reusing the same handle, makes
  libcurl wrongl…
severity: critical
cvss: 9.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'
cwe:
  - CWE-294
  - CWE-201
vendor: haxx
product: curl
affected:
  - 'curl >= 7.10.6, < 8.21.0'
patched:
  - curl 8.21.0
published: '2026-07-03'
updated: '2026-09-15'
sourceUpdated: '2026-09-15T07:16:25.870'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-11856'
references:
  - url: 'https://curl.se/docs/CVE-2026-11856.html'
    label: 2499f714-1537-4658-8207-48ae4bb9eae9
  - url: 'https://curl.se/docs/CVE-2026-11856.json'
    label: 2499f714-1537-4658-8207-48ae4bb9eae9
  - url: 'https://hackerone.com/reports/3793260'
    label: 2499f714-1537-4658-8207-48ae4bb9eae9
  - url: 'https://hackerone.com/reports/3793260'
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-11856.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-11856'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2496767'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-11856'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-11856'
  - url: 'https://access.redhat.com/errata/RHSA-2026:69125'
  - url: 'https://access.redhat.com/errata/RHSA-2026:34975'
  - url: 'https://access.redhat.com/errata/RHSA-2026:29017'
tags:
  - nvd
  - cve.org
  - exploit-available
  - csaf
  - vex
  - red-hat
  - score-dispute
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'yes'
  technicalImpact: total
  timestamp: '2026-07-06T18:22:46.260282Z'
epss: 0.00688
epssPercentile: 0.50667
ingestedAt: '2026-07-04T04:55:39.425Z'
scores:
  nvd: 9.8
  vendor: 6.5
---

## Overview

Successfully using libcurl to do a transfer to a specific HTTP origin
(`hostA`) with **Digest** authentication and then changing the origin to a
different one (`hostB`) for a second transfer, reusing the same handle, makes
libcurl wrongly pass on the `Authorization:` header field meant for `hostA`,
to `hostB`.

## Affected

- `curl >= 7.10.6, < 8.21.0`

## Remediation

Upgrade past the affected range:

- `curl 8.21.0`

## Vendor advisories

- **RHSA-2026:69125** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux BaseOS (v. 10) · released 2026-09-21 · [advisory](https://access.redhat.com/errata/RHSA-2026:69125)
- **RHSA-2026:34975** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-07-02 · [advisory](https://access.redhat.com/errata/RHSA-2026:34975)
- **RHSA-2026:29017** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-06-24 · [advisory](https://access.redhat.com/errata/RHSA-2026:29017)
- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat OpenShift Container Platform 4, Red Hat Enterprise Linux 8, … · updated 2026-09-21 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-11856.json)