CVE-2026-86863 pgAdmin 4: Authentication bypass via a client-controlled identity header in Webserver authentication mode
Attackers can bypass authentication in pgAdmin 4 by spoofing identity headers when webserver authentication is enabled, gaining administrator access.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-86863?
CVE-2026-86863 is a critical authentication bypass vulnerability in pgadmin.org pgAdmin 4, published on 17 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-86863?
It affects 1 product.
Products include Pgadmin Pgadmin 4.
How do I fix CVE-2026-86863?
No fix has been published for CVE-2026-86863 yet. Limit exposure of the affected software until one is available.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-86863 being exploited?
There is no known exploitation of CVE-2026-86863 in the wild and no public exploit code.
Other vulnerabilities in pgadmin.org pgAdmin 4
- CVE-2025-2945 pgAdmin 4: Remote Code Execution in Query Tool and Cloud Deployment
- CVE-2024-9014 OAuth2 client id and secret exposed through the web browser in pgAdmin 4
- CVE-2026-12046 Deserialization in pgAdmin 4
- CVE-2026-17351 SQL injection in pgAdmin 4
- CVE-2026-17566 Command injection in pgAdmin 4
Sources
Also known as GHSA-rc4w-fwh9-f5j9.