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CVE-2026-66339— Libsoup: libsoup: proxy credentials leak to destination server via proxy-authorization header in connect tunnels

Quick assessment

Affected
Red Hat Red Hat Enterprise Linux 10
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

libsoup是libsoup团队开源的一个HTTP库。 libsoup存在信息泄露漏洞，该漏洞源于在通过HTTP代理建立CONNECT隧道后错误地将Proxy-Authorization标头附加到后续HTTPS请求，导致目标服务器捕获代理凭据，造成信息泄露。

CVSS 6.5 · Medium EPSS 0.25% · P16

Affected Version Matrix 5

VendorProduct Version RangeStatus
Red Hat Red Hat Enterprise Linux 10 any affected
Red Hat Red Hat Enterprise Linux 6 any affected
Red Hat Red Hat Enterprise Linux 7 any affected
Red Hat Red Hat Enterprise Linux 8 any affected
Red Hat Red Hat Enterprise Linux 9 any affected
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I. Basic Information for CVE-2026-66339

Vulnerability Information
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Vulnerability Title
Libsoup: libsoup: proxy credentials leak to destination server via proxy-authorization header in connect tunnels
Source: CVE Program / CVE List V5
Vulnerability Description
A flaw was found in libsoup. After a CONNECT tunnel is established through an HTTP proxy, libsoup incorrectly attaches the Proxy-Authorization header to subsequent HTTPS requests sent through that tunnel to the destination server. This allows the destination server to capture proxy credentials, leading to information disclosure.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
通过发送数据的信息暴露
Source: CVE Program / CVE List V5
Vulnerability Title
libsoup 信息泄露漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
libsoup是libsoup团队开源的一个HTTP库。 libsoup存在信息泄露漏洞，该漏洞源于在通过HTTP代理建立CONNECT隧道后错误地将Proxy-Authorization标头附加到后续HTTPS请求，导致目标服务器捕获代理凭据，造成信息泄露。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Red Hat Red Hat Enterprise Linux 10 - cpe:/a:redhat:enterprise_linux:10
Red Hat Red Hat Enterprise Linux 6 - cpe:/o:redhat:rhel_els:6
Red Hat Red Hat Enterprise Linux 7 - cpe:/o:redhat:rhel_els:7
Red Hat Red Hat Enterprise Linux 8 - cpe:/a:redhat:enterprise_linux:8
Red Hat Red Hat Enterprise Linux 9 - cpe:/a:redhat:enterprise_linux:9

II. Public POCs for CVE-2026-66339

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III. Intelligence Information for CVE-2026-66339

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Vendor Advisories for CVE-2026-66339 (2)

Same Patch Batch · Red Hat · 2026-07-24 · 10 CVEs total

CVE-2026-17107 8.5 HIGH Cluster-proxy: impersonation-header injection grants cluster-admin on every managed cluste
CVE-2026-66337 6.5 MEDIUM Libsoup: libsoup: heap buffer over-read via integer underflow in soup_filter_input_stream_
CVE-2026-17059 6.5 MEDIUM Keycloak-services: keycloak-services: information disclosure via role-users endpoint bypas
CVE-2026-17048 5.5 MEDIUM Keycloak-services: keycloak-services: vault-resolved rotated client secrets leaked via adm
CVE-2026-16743 5.5 MEDIUM Accountsservice: accountsservice: arbitrary file read via seticonfile for systemd-homed us
CVE-2026-16730 5.5 MEDIUM Dbus-broker: dbus-broker: session bus denial of service via emfile during peer setup
CVE-2026-16910 5.5 MEDIUM Quay: ssrf in red hat quay notification webhooks (slack/generic)
CVE-2026-66338 5.4 MEDIUM Libsoup: libsoup: http request smuggling via permissive chunk-size parsing in soup_body_in
CVE-2026-17039 3.1 LOW Pki-core: dogtag-pki: redhat-pki: pki-core: ca renewal request processing omits realm auth

IV. Related Vulnerabilities

Same product: Red Hat Enterprise Linux 10
Same vendor: Red Hat
Same weakness: CWE-201