diff --git a/services/security/dependency_scanner.go b/services/security/dependency_scanner.go
new file mode 100644
index 0000000000..b5773abbfd
--- /dev/null
+++ b/services/security/dependency_scanner.go
@@ -0,0 +1,541 @@
+// Copyright 2026 Moko Consulting <hello@mokoconsulting.tech>
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package security
+
+import (
+	"bytes"
+	"crypto/sha256"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"strings"
+	"time"
+
+	security_model "code.mokoconsulting.tech/MokoConsulting/MokoGitea/models/security"
+	"code.mokoconsulting.tech/MokoConsulting/MokoGitea/modules/git"
+	"code.mokoconsulting.tech/MokoConsulting/MokoGitea/modules/log"
+)
+
+// ──────────────────────────────────────────────────────────────────────
+// Dependency manifest parsers
+// ──────────────────────────────────────────────────────────────────────
+
+// dependency represents a single package with version.
+type dependency struct {
+	Name      string
+	Version   string
+	Ecosystem string // "Go", "npm", "PyPI", "Packagist"
+	FilePath  string // which manifest file it came from
+}
+
+// manifestParser extracts dependencies from a file's contents.
+type manifestParser struct {
+	FileName  string
+	Ecosystem string
+	Parse     func(content string, filePath string) []dependency
+}
+
+var manifestParsers = []manifestParser{
+	{"go.mod", "Go", parseGoMod},
+	{"package.json", "npm", parsePackageJSON},
+	{"composer.json", "Packagist", parseComposerJSON},
+	{"requirements.txt", "PyPI", parseRequirementsTxt},
+}
+
+// parseGoMod extracts dependencies from go.mod.
+func parseGoMod(content, filePath string) []dependency {
+	var deps []dependency
+	inRequire := false
+
+	for _, line := range strings.Split(content, "\n") {
+		line = strings.TrimSpace(line)
+
+		if line == ")" {
+			inRequire = false
+			continue
+		}
+		if strings.HasPrefix(line, "require (") || strings.HasPrefix(line, "require(") {
+			inRequire = true
+			continue
+		}
+
+		if inRequire {
+			// Lines like: github.com/foo/bar v1.2.3
+			parts := strings.Fields(line)
+			if len(parts) >= 2 && !strings.HasPrefix(parts[0], "//") {
+				deps = append(deps, dependency{
+					Name:      parts[0],
+					Version:   parts[1],
+					Ecosystem: "Go",
+					FilePath:  filePath,
+				})
+			}
+			continue
+		}
+
+		// Single-line require: require github.com/foo/bar v1.2.3
+		if strings.HasPrefix(line, "require ") && !strings.Contains(line, "(") {
+			parts := strings.Fields(line)
+			if len(parts) >= 3 {
+				deps = append(deps, dependency{
+					Name:      parts[1],
+					Version:   parts[2],
+					Ecosystem: "Go",
+					FilePath:  filePath,
+				})
+			}
+		}
+	}
+	return deps
+}
+
+// parsePackageJSON extracts dependencies from package.json.
+func parsePackageJSON(content, filePath string) []dependency {
+	var pkg struct {
+		Dependencies    map[string]string `json:"dependencies"`
+		DevDependencies map[string]string `json:"devDependencies"`
+	}
+	if err := json.Unmarshal([]byte(content), &pkg); err != nil {
+		return nil
+	}
+
+	var deps []dependency
+	for name, version := range pkg.Dependencies {
+		deps = append(deps, dependency{
+			Name:      name,
+			Version:   cleanSemver(version),
+			Ecosystem: "npm",
+			FilePath:  filePath,
+		})
+	}
+	for name, version := range pkg.DevDependencies {
+		deps = append(deps, dependency{
+			Name:      name,
+			Version:   cleanSemver(version),
+			Ecosystem: "npm",
+			FilePath:  filePath,
+		})
+	}
+	return deps
+}
+
+// parseComposerJSON extracts dependencies from composer.json.
+func parseComposerJSON(content, filePath string) []dependency {
+	var pkg struct {
+		Require    map[string]string `json:"require"`
+		RequireDev map[string]string `json:"require-dev"`
+	}
+	if err := json.Unmarshal([]byte(content), &pkg); err != nil {
+		return nil
+	}
+
+	var deps []dependency
+	for name, version := range pkg.Require {
+		if name == "php" || strings.HasPrefix(name, "ext-") {
+			continue // skip platform requirements
+		}
+		deps = append(deps, dependency{
+			Name:      name,
+			Version:   cleanSemver(version),
+			Ecosystem: "Packagist",
+			FilePath:  filePath,
+		})
+	}
+	for name, version := range pkg.RequireDev {
+		if name == "php" || strings.HasPrefix(name, "ext-") {
+			continue
+		}
+		deps = append(deps, dependency{
+			Name:      name,
+			Version:   cleanSemver(version),
+			Ecosystem: "Packagist",
+			FilePath:  filePath,
+		})
+	}
+	return deps
+}
+
+// parseRequirementsTxt extracts dependencies from requirements.txt.
+func parseRequirementsTxt(content, filePath string) []dependency {
+	var deps []dependency
+	for _, line := range strings.Split(content, "\n") {
+		line = strings.TrimSpace(line)
+		if line == "" || strings.HasPrefix(line, "#") || strings.HasPrefix(line, "-") {
+			continue
+		}
+
+		// Handle: package==1.0.0, package>=1.0.0, package~=1.0.0
+		for _, sep := range []string{"==", ">=", "~=", "<=", "!="} {
+			if idx := strings.Index(line, sep); idx > 0 {
+				name := strings.TrimSpace(line[:idx])
+				version := strings.TrimSpace(line[idx+len(sep):])
+				// Strip any trailing constraints like ",<2.0"
+				if ci := strings.Index(version, ","); ci > 0 {
+					version = version[:ci]
+				}
+				deps = append(deps, dependency{
+					Name:      name,
+					Version:   version,
+					Ecosystem: "PyPI",
+					FilePath:  filePath,
+				})
+				break
+			}
+		}
+	}
+	return deps
+}
+
+// cleanSemver strips npm/composer range prefixes (^, ~, >=) to get a plain version.
+func cleanSemver(v string) string {
+	v = strings.TrimSpace(v)
+	v = strings.TrimLeft(v, "^~>=<!")
+	v = strings.TrimSpace(v)
+	// If it has " || " or " - " (ranges), take the first version
+	if idx := strings.Index(v, " "); idx > 0 {
+		v = v[:idx]
+	}
+	return v
+}
+
+// ──────────────────────────────────────────────────────────────────────
+// OSV.dev API client
+// ──────────────────────────────────────────────────────────────────────
+
+const osvBatchURL = "https://api.osv.dev/v1/querybatch"
+const osvMaxBatch = 1000 // OSV batch limit
+
+var osvClient = &http.Client{Timeout: 30 * time.Second}
+
+// osvQuery is a single query in a batch request.
+type osvQuery struct {
+	Package *osvPackage `json:"package"`
+	Version string      `json:"version"`
+}
+
+type osvPackage struct {
+	Name      string `json:"name"`
+	Ecosystem string `json:"ecosystem"`
+}
+
+// osvBatchRequest is the batch query body.
+type osvBatchRequest struct {
+	Queries []osvQuery `json:"queries"`
+}
+
+// osvBatchResponse is the batch response.
+type osvBatchResponse struct {
+	Results []osvResult `json:"results"`
+}
+
+type osvResult struct {
+	Vulns []osvVuln `json:"vulns"`
+}
+
+type osvVuln struct {
+	ID       string        `json:"id"`
+	Summary  string        `json:"summary"`
+	Details  string        `json:"details"`
+	Severity []osvSeverity `json:"severity"`
+	Aliases  []string      `json:"aliases"`
+}
+
+type osvSeverity struct {
+	Type  string `json:"type"`  // "CVSS_V3", "CVSS_V2"
+	Score string `json:"score"` // CVSS vector string
+}
+
+// queryOSV sends a batch of dependencies to OSV.dev and returns vulnerabilities.
+func queryOSV(deps []dependency) (*osvBatchResponse, error) {
+	queries := make([]osvQuery, 0, len(deps))
+	for _, d := range deps {
+		if d.Version == "" || d.Version == "*" || d.Version == "latest" {
+			continue // can't query without a concrete version
+		}
+		queries = append(queries, osvQuery{
+			Package: &osvPackage{Name: d.Name, Ecosystem: d.Ecosystem},
+			Version: d.Version,
+		})
+	}
+
+	if len(queries) == 0 {
+		return &osvBatchResponse{}, nil
+	}
+
+	body, err := json.Marshal(osvBatchRequest{Queries: queries})
+	if err != nil {
+		return nil, fmt.Errorf("marshal OSV request: %w", err)
+	}
+
+	resp, err := osvClient.Post(osvBatchURL, "application/json", bytes.NewReader(body))
+	if err != nil {
+		return nil, fmt.Errorf("OSV API request: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		respBody, _ := io.ReadAll(io.LimitReader(resp.Body, 1024))
+		return nil, fmt.Errorf("OSV API returned %d: %s", resp.StatusCode, string(respBody))
+	}
+
+	var result osvBatchResponse
+	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
+		return nil, fmt.Errorf("decode OSV response: %w", err)
+	}
+	return &result, nil
+}
+
+// ──────────────────────────────────────────────────────────────────────
+// Severity mapping
+// ──────────────────────────────────────────────────────────────────────
+
+// mapCVSSSeverity converts a CVSS v3 base score to an AlertSeverity.
+func mapCVSSSeverity(vulnSeverities []osvSeverity) security_model.AlertSeverity {
+	for _, s := range vulnSeverities {
+		if s.Type == "CVSS_V3" {
+			score := extractCVSSBaseScore(s.Score)
+			switch {
+			case score >= 9.0:
+				return security_model.SeverityCritical
+			case score >= 7.0:
+				return security_model.SeverityHigh
+			case score >= 4.0:
+				return security_model.SeverityMedium
+			case score > 0:
+				return security_model.SeverityLow
+			}
+		}
+	}
+
+	// No CVSS score available - default to medium
+	return security_model.SeverityMedium
+}
+
+// extractCVSSBaseScore parses the base score from a CVSS v3 vector string.
+// Vector format: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
+// We compute a simplified score from the vector metrics.
+func extractCVSSBaseScore(vector string) float64 {
+	if vector == "" {
+		return 0
+	}
+
+	// CVSS v3 vectors encode severity in metrics. Use a simplified
+	// lookup based on the most impactful metrics.
+	parts := make(map[string]string)
+	for _, segment := range strings.Split(vector, "/") {
+		kv := strings.SplitN(segment, ":", 2)
+		if len(kv) == 2 {
+			parts[kv[0]] = kv[1]
+		}
+	}
+
+	// Simplified scoring based on key CVSS v3 metrics
+	var score float64
+
+	// Attack Vector (AV)
+	switch parts["AV"] {
+	case "N": // Network
+		score += 3.0
+	case "A": // Adjacent
+		score += 2.0
+	case "L": // Local
+		score += 1.0
+	case "P": // Physical
+		score += 0.5
+	}
+
+	// Attack Complexity (AC)
+	switch parts["AC"] {
+	case "L": // Low
+		score += 1.5
+	case "H": // High
+		score += 0.5
+	}
+
+	// Privileges Required (PR)
+	switch parts["PR"] {
+	case "N": // None
+		score += 1.5
+	case "L": // Low
+		score += 1.0
+	case "H": // High
+		score += 0.5
+	}
+
+	// Impact metrics (C/I/A)
+	for _, metric := range []string{"C", "I", "A"} {
+		switch parts[metric] {
+		case "H":
+			score += 1.2
+		case "L":
+			score += 0.5
+		}
+	}
+
+	// Cap at 10.0
+	if score > 10.0 {
+		score = 10.0
+	}
+	return score
+}
+
+// ──────────────────────────────────────────────────────────────────────
+// DependencyScanner
+// ──────────────────────────────────────────────────────────────────────
+
+// DependencyScanner checks project dependencies against known vulnerabilities.
+type DependencyScanner struct{}
+
+// NewDependencyScanner creates a new dependency vulnerability scanner.
+func NewDependencyScanner() *DependencyScanner {
+	return &DependencyScanner{}
+}
+
+func (s *DependencyScanner) Type() security_model.ScannerType {
+	return security_model.ScannerDependency
+}
+
+func (s *DependencyScanner) ScanCommit(commit *git.Commit) ([]Finding, error) {
+	return s.ScanTree(commit)
+}
+
+func (s *DependencyScanner) ScanTree(commit *git.Commit) ([]Finding, error) {
+	if commit == nil {
+		return nil, nil
+	}
+
+	// Step 1: Find and parse manifest files
+	entries, err := commit.ListEntriesRecursiveFast()
+	if err != nil {
+		return nil, fmt.Errorf("ListEntriesRecursiveFast: %w", err)
+	}
+
+	var allDeps []dependency
+	for _, entry := range entries {
+		if !entry.IsRegular() {
+			continue
+		}
+
+		path := entry.Name()
+		baseName := path
+		if idx := strings.LastIndex(path, "/"); idx >= 0 {
+			baseName = path[idx+1:]
+		}
+
+		// Skip vendored/nested files
+		lower := strings.ToLower(path)
+		if strings.Contains(lower, "vendor/") || strings.Contains(lower, "node_modules/") ||
+			strings.Contains(lower, "testdata/") {
+			continue
+		}
+
+		for _, parser := range manifestParsers {
+			if baseName == parser.FileName {
+				reader, err := entry.Blob().DataAsync()
+				if err != nil {
+					log.Trace("DependencyScanner: skip %s: %v", path, err)
+					continue
+				}
+				content, err := io.ReadAll(io.LimitReader(reader, 5*1024*1024)) // 5MB limit
+				reader.Close()
+				if err != nil {
+					continue
+				}
+
+				deps := parser.Parse(string(content), path)
+				allDeps = append(allDeps, deps...)
+				break
+			}
+		}
+	}
+
+	if len(allDeps) == 0 {
+		return nil, nil
+	}
+
+	log.Info("DependencyScanner: found %d dependencies across manifest files", len(allDeps))
+
+	// Step 2: Query OSV in batches
+	var findings []Finding
+	for i := 0; i < len(allDeps); i += osvMaxBatch {
+		end := i + osvMaxBatch
+		if end > len(allDeps) {
+			end = len(allDeps)
+		}
+		batch := allDeps[i:end]
+
+		resp, err := queryOSV(batch)
+		if err != nil {
+			log.Error("DependencyScanner: OSV query failed: %v", err)
+			continue
+		}
+
+		// Step 3: Map results to findings
+		// OSV batch response indices correspond 1:1 with the query indices.
+		// But we may have skipped deps with empty versions, so build the
+		// queryable subset to align indices.
+		queryable := make([]dependency, 0, len(batch))
+		for _, d := range batch {
+			if d.Version != "" && d.Version != "*" && d.Version != "latest" {
+				queryable = append(queryable, d)
+			}
+		}
+
+		for j, result := range resp.Results {
+			if j >= len(queryable) {
+				break
+			}
+			dep := queryable[j]
+
+			for _, vuln := range result.Vulns {
+				severity := mapCVSSSeverity(vuln.Severity)
+
+				// Build CVE alias for rule ID (prefer CVE over GHSA)
+				ruleID := vuln.ID
+				for _, alias := range vuln.Aliases {
+					if strings.HasPrefix(alias, "CVE-") {
+						ruleID = alias
+						break
+					}
+				}
+
+				title := fmt.Sprintf("%s in %s@%s", ruleID, dep.Name, dep.Version)
+
+				description := vuln.Summary
+				if description == "" {
+					description = vuln.Details
+				}
+				// Truncate long descriptions
+				if len(description) > 500 {
+					description = description[:497] + "..."
+				}
+
+				// Metadata JSON
+				meta, _ := json.Marshal(map[string]string{
+					"vuln_id":   vuln.ID,
+					"ecosystem": dep.Ecosystem,
+					"package":   dep.Name,
+					"version":   dep.Version,
+				})
+
+				fingerprint := fmt.Sprintf("%x", sha256.Sum256([]byte(vuln.ID+":"+dep.Name+":"+dep.Version)))
+
+				findings = append(findings, Finding{
+					Scanner:     security_model.ScannerDependency,
+					Severity:    severity,
+					RuleID:      ruleID,
+					Title:       title,
+					Description: description,
+					FilePath:    dep.FilePath,
+					CommitSHA:   commit.ID.String(),
+					Fingerprint: fingerprint[:32],
+					Metadata:    string(meta),
+				})
+			}
+		}
+	}
+
+	return findings, nil
+}
diff --git a/services/security/orchestrator.go b/services/security/orchestrator.go
index a44c9c1b73..f4108d9a89 100644
--- a/services/security/orchestrator.go
+++ b/services/security/orchestrator.go
@@ -32,8 +32,10 @@ func ScanOnPush(ctx context.Context, repo *repo_model.Repository, commit *git.Co
 	if cfg.SecretScanner {
 		scanners = append(scanners, NewSecretScanner())
 	}
+	if cfg.DependScanner {
+		scanners = append(scanners, NewDependencyScanner())
+	}
 	// Future scanners added here:
-	// if cfg.DependScanner { scanners = append(scanners, NewDependencyScanner()) }
 	// if cfg.CodeScanner { scanners = append(scanners, NewCodeScanner()) }
 
 	if len(scanners) == 0 {