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.

326,895

Total vulnerabilities in the database

CVE-2026-30857

Summary

A cross-tenant authorization bypass in the knowledge base copy endpoint allows any authenticated user to clone (duplicate) another tenant’s knowledge base into their own tenant by knowing/guessing the source knowledge base ID. This enables bulk data exfiltration (document/FAQ content) across tenants, making the impact critical.

Details

The POST /api/v1/knowledge-bases/copy endpoint enqueues an asynchronous KB clone task using the caller-supplied source_id without verifying ownership (see internal/handler/knowledgebase.go).

// Create KB clone payload
payload := types.KBClonePayload{
  TenantID: tenantID.(uint64),
  TaskID:   taskID,
  SourceID: req.SourceID, // from attacker&#039;s input
  TargetID: req.TargetID,
}

payloadBytes, err := json.Marshal(payload)
if err != nil {
  logger.Errorf(ctx, &quot;Failed to marshal KB clone payload: %v&quot;, err)
  c.Error(errors.NewInternalServerError(&quot;Failed to create task&quot;))
  return
}

// Enqueue KB clone task to Asynq
task := asynq.NewTask(types.TypeKBClone, payloadBytes,
asynq.TaskID(taskID), asynq.Queue(&quot;default&quot;), asynq.MaxRetry(3)) // enqueue task
info, err := h.asynqClient.Enqueue(task)
if err != nil {
  logger.Errorf(ctx, &quot;Failed to enqueue KB clone task: %v&quot;, err)
  c.Error(errors.NewInternalServerError(&quot;Failed to enqueue task&quot;))
  return
}

Then, the asynq task handler (ProcessKBClone) invokes the CopyKnowledgeBase service method to perform the clone operation (see internal/application/service/knowledge.go):

// Get source and target knowledge bases
srcKB, dstKB, err := s.kbService.CopyKnowledgeBase(ctx, payload.SourceID, payload.TargetID)
if err != nil {
    logger.Errorf(ctx, &quot;Failed to copy knowledge base: %v&quot;, err)
    handleError(progress, err, &quot;Failed to copy knowledge base configuration&quot;)
    return err
}

After that, the CopyKnowledgeBase method calls the repository method to load the source knowledge base (see internal/application/service/knowledgebase.go):

func (s *knowledgeBaseService) CopyKnowledgeBase(ctx context.Context,
	srcKB string, dstKB string,
) (*types.KnowledgeBase, *types.KnowledgeBase, error) {
	sourceKB, err := s.repo.GetKnowledgeBaseByID(ctx, srcKB)
	if err != nil {
		logger.Errorf(ctx, &quot;Get source knowledge base failed: %v&quot;, err)
		return nil, nil, err
	}
	sourceKB.EnsureDefaults()
	tenantID := ctx.Value(types.TenantIDContextKey).(uint64)
	var targetKB *types.KnowledgeBase
	if dstKB != &quot;&quot; {
		targetKB, err = s.repo.GetKnowledgeBaseByID(ctx, dstKB)
        // ...
    }
    // ...
}

> Note: until now, the tenant ID is correctly set in context to the attacker’s tenant (from the payload), which can be used to prevent cross-tenant access.

However, the repository method GetKnowledgeBaseByID loads knowledge bases by id only, allowing cross-tenant reads (see internal/application/repository/knowledgebase.go).

func (r *knowledgeBaseRepository) GetKnowledgeBaseByID(ctx context.Context, id string) (*types.KnowledgeBase, error) {
	var kb types.KnowledgeBase
	if err := r.db.WithContext(ctx).Where(&quot;id = ?&quot;, id).First(&amp;kb).Error; err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, ErrKnowledgeBaseNotFound
		}
		return nil, err
	}
	return &amp;kb, nil
}

The data access layer fails to enforce tenant isolation because GetKnowledgeBaseByID only filters by ID and ignores the tenant_id present in the context. A secure implementation should enforce a tenant-scoped lookup (e.g., WHERE id = ? AND tenant_id = ?) or use a tenant-aware repository API to prevent cross-tenant access.

Service shallow-copies the KB configuration by calling GetKnowledgeBaseByID(ctx, srcKB) for the source KB, then creates a new KB under the attacker’s tenant while copying fields from the victim KB (internal/application/service/knowledgebase.go):

sourceKB, err := s.repo.GetKnowledgeBaseByID(ctx, srcKB) // not tenant-scoped
...
targetKB = &amp;types.KnowledgeBase{
    ID:                    uuid.New().String(),
    Name:                  sourceKB.Name,
    Type:                  sourceKB.Type,
    Description:           sourceKB.Description,
    TenantID:              tenantID,
    ChunkingConfig:        sourceKB.ChunkingConfig,
    ImageProcessingConfig: sourceKB.ImageProcessingConfig,
    EmbeddingModelID:      sourceKB.EmbeddingModelID,
    SummaryModelID:        sourceKB.SummaryModelID,
    VLMConfig:             sourceKB.VLMConfig,
    StorageConfig:         sourceKB.StorageConfig,
    FAQConfig:             faqConfig,
}
targetKB.EnsureDefaults()
  if err := s.repo.CreateKnowledgeBase(ctx, targetKB); err != nil {
      return nil, nil, err
  }
}

PoC

Precondition: Attacker is authenticated in Tenant A and can obtain (or guess) a victim's knowledge base UUID belonging to Tenant B.

Authenticate as Tenant A and obtain a bearer token or API key.
Start a cross-tenant clone using the victim’s knowledge base ID as source_id:

curl -X POST http://localhost:8088/api/v1/knowledge-bases/copy \
  -H &quot;Authorization: Bearer &lt;ATTACKER_TOKEN&gt;&quot; \
  -H &quot;Content-Type: application/json&quot; \
  -d &#039;{&quot;source_id&quot;:&quot;&lt;VICTIM_KB_UUID&gt;&quot;,&quot;target_id&quot;:&quot;&quot;}&#039;

Observe that the task is accepted:

HTTP 200 OK
Response contains a task_id and a message like "Knowledge base copy task started".

After the async task completes, a new knowledge base appears under Tenant A containing copied content/config from Tenant B.

> Note: the copy can succeed even when models referenced by the source KB do not exist in the attacker tenant, indicating the workflow does not validate model ownership during copy.

PoC Video:

https://github.com/user-attachments/assets/8313fa44-5d5d-43f4-8ebd-f465c5a9d56e

Impact

This is a Broken Access Control (BOLA/IDOR) vulnerability enabling cross-tenant data exfiltration:

Any authenticated user can trigger a clone of a victim tenant’s knowledge base into their own tenant.
Results in bulk disclosure/duplication of knowledge base contents (documents/FAQ entries/chunks), plus associated configuration.

Published: Mar 6, 2026
Updated: Mar 7, 2026
CVE: CVE-2026-30857
GHSA: GHSA-8rf9-c59g-f82f
Severity: Medium
Exploit:

CVSS v3:

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

CWEs:

CWE-639

OWASP TOP 10:

A5 - Broken Access Control

Affected Software
References

Software	From	Fixed in
github.com/Tencent/WeKnora	-	0.2.14.x

https://github.com/Tencent/WeKnora/security/advisories/GHSA-8rf9-c59g-f82f

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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.