How should we interpret CVSS severity scores?

CVSS estimates technical severity, but it does not automatically equal business risk. Prioritize using context like internet exposure, asset criticality, known exploitation, and whether compensating controls exist. A Medium CVSS on an exposed production system can be more urgent than a Critical on an isolated non-production host.

Vulnerability Database

Q: What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

Q: What's the difference between a vulnerability, an exploit, and a zero-day?

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. Risk increases sharply when exploitation becomes reliable or widespread.

Q: Why do vulnerabilities keep reappearing in our environment?

Recurring findings usually come from incomplete asset discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host.

Q: How do we prioritize remediation without burning out the team?

Use a repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress so remediation is steady, not reactive.

Q: How can SynScan help reduce vulnerability risk over time?

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.

352,262

Total vulnerabilities in the database

CVE-2026-25119 — gogs.io/gogs

Authentication Bypass by Spoofing

Summary

When ENABLE_REVERSE_PROXY_AUTHENTICATION is enabled, Gogs accepts the configured authentication header (default: X-WEBAUTH-USER) directly from client requests without validating that the request originated from a trusted reverse proxy. Any remote attacker who can reach the Gogs service can forge this header to impersonate any user or trigger automatic account creation, completely bypassing authentication.

Root Cause

The vulnerability exists because Gogs reads the authentication header directly from the incoming HTTP request without any verification that the header was set by a trusted reverse proxy.

Vulnerable Code Flow

In internal/context/auth.go lines 206-234:

func authenticatedUser(store AuthStore, ctx *macaron.Context, sess session.Store) (_ *database.User, isBasicAuth, isTokenAuth bool) {
    // ... existing auth checks ...

    if uid &lt;= 0 {
        if conf.Auth.EnableReverseProxyAuthentication {
            // Reads header DIRECTLY from client request - NO VALIDATION!
            webAuthUser := ctx.Req.Header.Get(conf.Auth.ReverseProxyAuthenticationHeader)
            if len(webAuthUser) &gt; 0 {
                user, err := store.GetUserByUsername(ctx.Req.Context(), webAuthUser)
                if err != nil {
                    if !database.IsErrUserNotExist(err) {
                        log.Error(&quot;Failed to get user by name: %v&quot;, err)
                        return nil, false, false
                    }

                    // Check if enabled auto-registration.
                    if conf.Auth.EnableReverseProxyAutoRegistration {
                        // Creates new user with forged username!
                        user, err = store.CreateUser(
                            ctx.Req.Context(),
                            webAuthUser,
                            gouuid.NewV4().String()+&quot;@localhost&quot;,
                            database.CreateUserOptions{
                                Activated: true,
                            },
                        )
                        if err != nil {
                            log.Error(&quot;Failed to create user %q: %v&quot;, webAuthUser, err)
                            return nil, false, false
                        }
                    }
                }
                // Returns user as authenticated without any verification!
                return user, false, false
            }
        }
        // ... fallback to basic auth ...
    }
    // ...
}

The code has zero validation that:

The request came through a reverse proxy
The header was set by the proxy (not the client)
Gogs is actually behind a reverse proxy
The direct access to Gogs is restricted

The vulnerability occurs when:

Gogs is publicly accessible (e.g., 0.0.0.0:3000)
ENABLE_REVERSE_PROXY_AUTHENTICATION = true

Proof of Concept

Prerequisites

Gogs instance with the following configuration in custom/conf/app.ini:

[auth]
ENABLE_REVERSE_PROXY_AUTHENTICATION = true

An attacker can impersonate any user including administrators:

# Become admin instantly
curl http://gogs.example.com/ -H &quot;X-WEBAUTH-USER: &lt;username&gt;&quot;

Recommended Fixes

Add validation to ensure headers come from trusted sources:

func authenticatedUser(store AuthStore, ctx *macaron.Context, sess session.Store) (_ *database.User, isBasicAuth, isTokenAuth bool) {
    // ... existing code ...

    if uid &lt;= 0 {
        if conf.Auth.EnableReverseProxyAuthentication {
            // Validate request is from trusted proxy
            if !isRequestFromTrustedProxy(ctx.Req) {
                log.Warn(&quot;Reverse proxy auth header received from untrusted source: %s&quot;, ctx.RemoteAddr())
                return nil, false, false
            }

            webAuthUser := ctx.Req.Header.Get(conf.Auth.ReverseProxyAuthenticationHeader)
            // ... rest of the code ...
        }
    }
    // ...
}

// New validation function
func isRequestFromTrustedProxy(req *http.Request) bool {
    // Check if request is from localhost/trusted IPs
    remoteIP := getRemoteIP(req)

    // Only accept from localhost by default
    if remoteIP.IsLoopback() {
        return true
    }

    // Check against configured trusted proxy IPs
    for _, trustedIP := range conf.Auth.TrustedProxyIPs {
        if remoteIP.String() == trustedIP {
            return true
        }
    }

    return false
}

Add configuration option:

[auth]
ENABLE_REVERSE_PROXY_AUTHENTICATION = false
REVERSE_PROXY_AUTHENTICATION_HEADER = X-WEBAUTH-USER
; Comma-separated list of trusted proxy IPs (default: 127.0.0.1)
TRUSTED_PROXY_IPS = 127.0.0.1,::1
; Whether to require trusted proxy validation (recommended: true)
REQUIRE_TRUSTED_PROXY = true

References

Published: Jun 22, 2026
Updated: Jun 23, 2026
CVE: CVE-2026-25119
GHSA: GHSA-w6j9-vw59-27wv
Severity: High
Exploit:
CISA KEV:

No technical information available.

CWEs:

CWE-290

Affected Software
References

Software	From	Fixed in
gogs.io/gogs	-	0.14.3

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Frequently Asked Questions

What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.