Detections
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libcurl 7.71.0 < 8.20.0 Cookie Leak via Stale Host Header

high Nessus Plugin ID 311420

Synopsis

The remote host has a program that is affected by a cookie leak vulnerability.

Description

The version of libcurl installed on the remote host is 7.71.0 prior to 8.20.0. It is, therefore, affected by a cookie leak vulnerability:

 - When using the same connection handle for multiple HTTP requests, if a custom Host: header is removed in a subsequent request, the second request would use stale information and pass on cookies meant for the first host in the second request. This primarily affects clear text HTTP transfers, as HTTPS connections require proper SNI configuration making the vulnerability less exploitable.
 (CVE-2026-6276)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

Solution

Upgrade libcurl to version 8.20.0 or later

See Also

https://curl.se/docs/CVE-2026-6276.html

Plugin Details

Severity: High

ID: 311420

File Name: libcurl_CVE-2026-6276.nasl

Version: 1.1

Type: Local

Agent: windows, macosx, unix

Family: Misc.

Published: 5/1/2026

Updated: 5/1/2026

Configuration: Enable thorough checks (optional)

Supported Sensors: Nessus Agent, Nessus

Risk Information

VPR

Risk Factor: High

Score: 7.4

CVSS v2

Risk Factor: Medium

Base Score: 5

Vector: CVSS2#AV:N/AC:L/Au:N/C:P/I:N/A:N

CVSS Score Source: CVE-2026-6276

CVSS v3

Risk Factor: High

Base Score: 7.5

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Vulnerability Information

CPE: cpe:/a:haxx:libcurl

Required KB Items: installed_sw/libcurl

Patch Publication Date: 4/29/2026

Vulnerability Publication Date: 4/29/2026

Reference Information

CVE: CVE-2026-6276

IAVA: 2026-A-0397