Description
pgAdmin 4's Webserver authentication source is intended to accept an identity asserted by the web server or reverse proxy in front of pgAdmin, delivered through the WSGI/CGI environment. WebserverAuthentication.get_user() read config.WEBSERVER_REMOTE_USER from request.environ and, when that returned nothing, fell back to reading the same name directly from the inbound HTTP request headers via request.headers.get(). An inbound HTTP header is written by whoever sends the request, so any client able to reach pgAdmin could supply that header itself and be authenticated as any username it named, including an existing Administrator, without presenting a password or any other credential. The environment lookup could also be satisfied by a client-supplied header whenever WEBSERVER_REMOTE_USER was configured to an HTTP_-prefixed or hyphenated name such as HTTP_X_FORWARDED_USER or X-Forwarded-User, since WSGI servers place inbound headers into the environment under exactly those names. Deployments are affected only when 'webserver' is enabled in AUTHENTICATION_SOURCES.

The fix distinguishes a genuine CGI/WSGI variable from a header-derived one and implicitly trusts only the former. A header-asserted identity is now accepted only when the operator explicitly opts in via WEBSERVER_REMOTE_USER_FROM_HEADER, the request arrives from a peer listed in WEBSERVER_TRUSTED_PROXIES, and, when configured, a shared secret supplied in WEBSERVER_SHARED_SECRET_HEADER matches WEBSERVER_SHARED_SECRET under a constant-time comparison. The trusted-peer check deliberately reads the real socket peer address rather than request.remote_addr, because ProxyFix rewrites the latter from the client-controlled X-Forwarded-For header and would otherwise allow an attacker to claim to be the trusted proxy. As defence in depth, login() now refuses any account whose auth_source is not 'webserver', so a misconfigured trust gate cannot be used to assume an internal or LDAP account.

This issue affects pgAdmin 4: from 6.2 before 9.18.
Published: 2026-09-17
Score: 9.3 Critical
EPSS: < 1% Very Low
KEV: No
Impact: Authentication bypass enabling unauthorized privilege escalation
Action: Immediate Patch
AI Analysis

Impact

The flaw allows a client to convince the pgAdmin 4 Webserver authentication mode to accept any user identity supplied in a custom HTTP header. The code mistakenly treats the header value as a trusted identity instead of a genuine WSGI environment variable, permitting authentication as, for example, an existing Administrator without any password. This falls under broken authentication weaknesses and leads to full credential impersonation.

Affected Systems

pgAdmin 4 deployed with authentication sources including 'webserver', affecting all versions from 6.2 up to but not including 9.18. The vulnerability applies only when the Webserver authentication mode is active, regardless of other authentication sources.

Risk and Exploitability

The exploit is trivial for a remote attacker who can reach the pgAdmin web interface; they can forge the required header and gain arbitrary user access without any credentials. If the application is publicly reachable, the likelihood of exploitation is high. The risk remains elevated until the installation is updated to a version that implements the guardrails described in the fix – namely, requiring a shared secret, validating proxy trust, and ensuring only CGI-derived environment variables are used for authentication.

Generated by OpenCVE AI on September 17, 2026 at 20:26 UTC.

Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

  • Upgrade pgAdmin 4 to version 9.18 or newer, which implements strict header validation, adds a shared secret mechanism, and restricts header‑derived identities to trusted proxies.
  • If a patch cannot be applied immediately, disable the 'webserver' authentication source or configure WEBSERVER_TRUSTED_PROXIES to include only known reverse‑proxy addresses, and enable WEBSERVER_SHARED_SECRET_HEADER with a strong secret.
  • Restrict network access to the pgAdmin web interface – use a firewall or VPN to limit connections to trusted IP ranges, ensuring that only authorized personnel can reach the web server.

Generated by OpenCVE AI on September 17, 2026 at 20:26 UTC.

Tracking

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Advisories

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History

Mon, 21 Sep 2026 17:45:00 +0000

Type Values Removed Values Added
CPEs cpe:2.3:a:pgadmin:pgadmin_4:*:*:*:*:*:postgresql:*:*

Thu, 17 Sep 2026 20:45:00 +0000

Type Values Removed Values Added
First Time appeared Pgadmin
Pgadmin pgadmin 4
Vendors & Products Pgadmin
Pgadmin pgadmin 4

Thu, 17 Sep 2026 16:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Thu, 17 Sep 2026 15:45:00 +0000

Type Values Removed Values Added
Description pgAdmin 4's Webserver authentication source is intended to accept an identity asserted by the web server or reverse proxy in front of pgAdmin, delivered through the WSGI/CGI environment. WebserverAuthentication.get_user() read config.WEBSERVER_REMOTE_USER from request.environ and, when that returned nothing, fell back to reading the same name directly from the inbound HTTP request headers via request.headers.get(). An inbound HTTP header is written by whoever sends the request, so any client able to reach pgAdmin could supply that header itself and be authenticated as any username it named, including an existing Administrator, without presenting a password or any other credential. The environment lookup could also be satisfied by a client-supplied header whenever WEBSERVER_REMOTE_USER was configured to an HTTP_-prefixed or hyphenated name such as HTTP_X_FORWARDED_USER or X-Forwarded-User, since WSGI servers place inbound headers into the environment under exactly those names. Deployments are affected only when 'webserver' is enabled in AUTHENTICATION_SOURCES. The fix distinguishes a genuine CGI/WSGI variable from a header-derived one and implicitly trusts only the former. A header-asserted identity is now accepted only when the operator explicitly opts in via WEBSERVER_REMOTE_USER_FROM_HEADER, the request arrives from a peer listed in WEBSERVER_TRUSTED_PROXIES, and, when configured, a shared secret supplied in WEBSERVER_SHARED_SECRET_HEADER matches WEBSERVER_SHARED_SECRET under a constant-time comparison. The trusted-peer check deliberately reads the real socket peer address rather than request.remote_addr, because ProxyFix rewrites the latter from the client-controlled X-Forwarded-For header and would otherwise allow an attacker to claim to be the trusted proxy. As defence in depth, login() now refuses any account whose auth_source is not 'webserver', so a misconfigured trust gate cannot be used to assume an internal or LDAP account. This issue affects pgAdmin 4: from 6.2 before 9.18.
Title pgAdmin 4: Authentication bypass via a client-controlled identity header in Webserver authentication mode
Weaknesses CWE-290
CWE-807
References
Metrics cvssV3_1

{'score': 9.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'}

cvssV4_0

{'score': 9.3, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N'}

Subscriptions

Pgadmin Pgadmin 4
cve-icon MITRE

Status: PUBLISHED

Assigner: PostgreSQL

Published:

Updated: 2026-09-17T16:01:16.146Z

Reserved: 2026-09-08T15:47:05.445Z

Link: CVE-2026-86863

cve-icon Vulnrichment

Updated: 2026-09-17T16:01:10.924Z

cve-icon NVD

Status : Analyzed

Published: 2026-09-17T16:18:17.863

Modified: 2026-09-21T17:27:28.303

Link: CVE-2026-86863

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-17T20:30:17Z

Weaknesses
  • CWE-290

    Authentication Bypass by Spoofing

  • CWE-807

    Reliance on Untrusted Inputs in a Security Decision