---
id: CVE-2026-8927
title: |-
  When reusing a libcurl handle for sequential transfers driven by
  environment-variable proxy configuration, libcurl fails to clear the proxy
  authentication state between requests
summary: |-
  When reusing a libcurl handle for sequential transfers driven by
  environment-variable proxy configuration, libcurl fails to clear the proxy
  authentication state between requests. Specifically, if the initial transfer
  authenticates agains…
severity: critical
cvss: 9.1
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N'
cwe:
  - CWE-294
  - CWE-201
vendor: haxx
product: curl
affected:
  - 'curl >= 7.12.0, < 8.21.0'
patched:
  - curl 8.21.0
published: '2026-07-03'
updated: '2026-09-15'
sourceUpdated: '2026-09-15T07:16:33.157'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-8927'
references:
  - url: 'https://curl.se/docs/CVE-2026-8927.html'
    label: 2499f714-1537-4658-8207-48ae4bb9eae9
  - url: 'https://curl.se/docs/CVE-2026-8927.json'
    label: 2499f714-1537-4658-8207-48ae4bb9eae9
  - url: 'https://hackerone.com/reports/3744543'
    label: 2499f714-1537-4658-8207-48ae4bb9eae9
  - url: 'https://hackerone.com/reports/3744543'
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-8927.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-8927'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2496769'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-8927'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-8927'
  - url: 'https://access.redhat.com/errata/RHSA-2026:55432'
  - url: 'https://access.redhat.com/errata/RHSA-2026:29017'
  - url: 'https://access.redhat.com/errata/RHSA-2026:34975'
  - url: 'https://access.redhat.com/errata/RHSA-2026:56869'
  - url: 'https://access.redhat.com/errata/RHSA-2026:69126'
tags:
  - nvd
  - cve.org
  - exploit-available
  - csaf
  - vex
  - red-hat
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-07-06T17:00:13.489405Z'
epss: 0.005
epssPercentile: 0.41922
ingestedAt: '2026-07-04T04:55:39.445Z'
scores:
  nvd: 9.1
  vendor: 7.5
---

## Overview

When reusing a libcurl handle for sequential transfers driven by
environment-variable proxy configuration, libcurl fails to clear the proxy
authentication state between requests. Specifically, if the initial transfer
authenticates against `proxyA` using Digest auth, a subsequent transfer routed
through `proxyB` erroneously leaks the `Proxy-Authorization:` header intended
solely for `proxyA`.

## Affected

- `curl >= 7.12.0, < 8.21.0`

## Remediation

Upgrade past the affected range:

- `curl 8.21.0`

## Vendor advisories

- **RHSA-2026:55432** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux BaseOS (v. 10) · released 2026-08-17 · [advisory](https://access.redhat.com/errata/RHSA-2026:55432)
- **RHSA-2026:29017** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-06-24 · [advisory](https://access.redhat.com/errata/RHSA-2026:29017)
- **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-2026:56869** · Red Hat · fixed in: Red Hat JBoss Core Services 2.4.62.SP5 · released 2026-08-19 · [advisory](https://access.redhat.com/errata/RHSA-2026:56869)
- **Red Hat VEX** · Important · affected: Confidential Compute Attestation, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, … · no fix planned: Red Hat Enterprise Linux 6, Confidential Compute Attestation, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 7, … · updated 2026-09-21 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-8927.json)
- **RHSA-2026:69126** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux BaseOS (v. 9) · released 2026-09-21 · [advisory](https://access.redhat.com/errata/RHSA-2026:69126)