diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
index 829a577..6971f63 100644
--- a/.github/workflows/codeql.yml
+++ b/.github/workflows/codeql.yml
@@ -31,7 +31,7 @@ jobs:
     - name: Set up Go
       uses: actions/setup-go@v6
       with:
-        go-version: '1.26.4'
+        go-version: '1.26.5'
 
     # Initialize CodeQL. If this fails with ECONNRESET locally, consider using --toolcache in act.
     - name: Initialize CodeQL
diff --git a/.github/workflows/go-ci.yml b/.github/workflows/go-ci.yml
index 61696ad..e2d421e 100644
--- a/.github/workflows/go-ci.yml
+++ b/.github/workflows/go-ci.yml
@@ -17,7 +17,7 @@ jobs:
     - name: Set up Go
       uses: actions/setup-go@v6
       with:
-        go-version: '1.26.4'
+        go-version: '1.26.5'
 
     - name: Build
       run: go build -v ./cmd/server
@@ -42,4 +42,4 @@ jobs:
         go install golang.org/x/vuln/cmd/govulncheck@latest
         govulncheck ./...
       env:
-        GOTOOLCHAIN: go1.26.4
+        GOTOOLCHAIN: go1.26.5
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 9fc209f..4aa010b 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -20,7 +20,7 @@ jobs:
       - name: Set up Go
         uses: actions/setup-go@v6
         with:
-          go-version: '1.26.4'
+          go-version: '1.26.5'
 
       - name: Run GoReleaser
         uses: goreleaser/goreleaser-action@v7
diff --git a/.jules/sentinel.md b/.jules/sentinel.md
index beda211..37ddc69 100644
--- a/.jules/sentinel.md
+++ b/.jules/sentinel.md
@@ -61,3 +61,8 @@
 **Vulnerability:** Not a direct vulnerability, but overly long handlers increase cognitive load and the likelihood of security-critical logic (like permission checks or input validation) being overlooked or bypassed during future maintenance.
 **Learning:** Modularizing complex handlers into distinct "parse", "authorize", and "dispatch" phases clarifies the security boundaries and ensures that each step (authentication, authorization, validation) must succeed before any state-changing action is taken.
 **Prevention:** Regularly refactor handlers that exceed a reasonable length (e.g., 50 lines) into smaller, single-responsibility methods.
+
+## 2024-07-27 - SSRF Protection on External Source URLs
+**Vulnerability:** The `AddExternalSource` handler in `internal/api/excluded_handlers.go` allowed unconstrained external URL submission without pre-flight checks, enabling potential Server-Side Request Forgery (SSRF) and Local Network sweeps.
+**Learning:** This codebase maintains its own purpose-built `blocklist/internal/security` package for validating SSRF. Using standard URL parsing is not enough when we need to intercept DNS rebinding and internal IP resolutions.
+**Prevention:** Always enforce URL schema limits and utilize the internal `security.IsSafeURL` function when validating user-provided external destinations before storing or fetching them.
diff --git a/go.mod b/go.mod
index 1b80d7c..200f6c3 100644
--- a/go.mod
+++ b/go.mod
@@ -1,6 +1,6 @@
 module blocklist
 
-go 1.26.4
+go 1.26.5
 
 require (
 	github.com/alicebob/miniredis/v2 v2.38.0
@@ -127,7 +127,7 @@ require (
 	golang.org/x/net v0.56.0 // indirect
 	golang.org/x/sync v0.21.0 // indirect
 	golang.org/x/sys v0.46.0 // indirect
-	golang.org/x/text v0.38.0 // indirect
+	golang.org/x/text v0.39.0 // indirect
 	golang.org/x/time v0.15.0 // indirect
 	google.golang.org/protobuf v1.36.11 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
diff --git a/go.sum b/go.sum
index 5bdc1de..68889a0 100644
--- a/go.sum
+++ b/go.sum
@@ -314,8 +314,8 @@ golang.org/x/sys v0.46.0 h1:noSf2Fq6F8DBgS+LysIkx7rIExoNHJsxOAtPp4rthXw=
 golang.org/x/sys v0.46.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=
 golang.org/x/term v0.44.0 h1:0rLvDRCtNj0gZkyIXhCyOb2OAzEhLVqc4B+hrsBhrmc=
 golang.org/x/term v0.44.0/go.mod h1:7ze4MdzUzLXpSAoFP1H0bOI9aXDqveSvatT5vKcFh2Y=
-golang.org/x/text v0.38.0 h1:sXmwo9DwP3OK9EZ7PqAdaooSGozfl/3a6/xJcbzPRhE=
-golang.org/x/text v0.38.0/go.mod h1:YXZt3QhHUKYT53r2lLKFIVi6Ao1jdzrTR/KQ09qyxF4=
+golang.org/x/text v0.39.0 h1:UbZz4pLOvn600D6Oh6GGEI6VAmndrEBLv8/6BEXzyus=
+golang.org/x/text v0.39.0/go.mod h1:3UwRclnC2g0TU9x8PZiyfOajCd1zaUNHF9cvqcQZ+ZM=
 golang.org/x/time v0.15.0 h1:bbrp8t3bGUeFOx08pvsMYRTCVSMk89u4tKbNOZbp88U=
 golang.org/x/time v0.15.0/go.mod h1:Y4YMaQmXwGQZoFaVFk4YpCt4FLQMYKZe9oeV/f4MSno=
 google.golang.org/protobuf v1.36.11 h1:fV6ZwhNocDyBLK0dj+fg8ektcVegBBuEolpbTQyBNVE=
diff --git a/internal/api/excluded_handlers.go b/internal/api/excluded_handlers.go
index 56de3e7..85ebf9f 100644
--- a/internal/api/excluded_handlers.go
+++ b/internal/api/excluded_handlers.go
@@ -10,6 +10,7 @@ import (
 	"time"
 
 	"blocklist/internal/models"
+	"blocklist/internal/security"
 
 	"github.com/gin-gonic/gin"
 	zlog "github.com/rs/zerolog/log"
@@ -290,6 +291,22 @@ func (h *APIHandler) AddExternalSource(c *gin.Context) {
 		return
 	}
 
+	// Security: Input length validation to prevent unconstrained resource consumption
+	if len(req.Name) > 255 || len(req.SourceType) > 255 {
+		c.JSON(http.StatusBadRequest, gin.H{"error": "Input fields exceed maximum length of 255 characters"})
+		return
+	}
+	if len(req.URL) > 2048 {
+		c.JSON(http.StatusBadRequest, gin.H{"error": "URL exceeds maximum length of 2048 characters"})
+		return
+	}
+
+	if err := security.IsSafeURL(req.URL); err != nil {
+		zlog.Warn().Err(err).Str("url", req.URL).Msg("Attempted to add unsafe external source URL")
+		c.JSON(http.StatusBadRequest, gin.H{"error": "Invalid or unsafe external source URL"})
+		return
+	}
+
 	src := models.ExternalSource{
 		Name:                 req.Name,
 		URL:                  req.URL,
diff --git a/internal/repository/postgres.go b/internal/repository/postgres.go
index 89989e2..01b5dd3 100644
--- a/internal/repository/postgres.go
+++ b/internal/repository/postgres.go
@@ -2,9 +2,9 @@ package repository
 
 import (
 	"blocklist/internal/models"
-	"github.com/bytedance/sonic"
 	"errors"
 	"fmt"
+	"github.com/bytedance/sonic"
 	"strconv"
 	"strings"
 	"time"
diff --git a/internal/repository/redis.go b/internal/repository/redis.go
index c82889a..909d3b9 100644
--- a/internal/repository/redis.go
+++ b/internal/repository/redis.go
@@ -4,8 +4,8 @@ import (
 	"context"
 	"crypto/rand"
 	"encoding/hex"
-	"github.com/bytedance/sonic"
 	"fmt"
+	"github.com/bytedance/sonic"
 	"strconv"
 	"strings"
 	"time"
diff --git a/internal/service/external_source_service.go b/internal/service/external_source_service.go
index 108598a..9cf8717 100644
--- a/internal/service/external_source_service.go
+++ b/internal/service/external_source_service.go
@@ -4,8 +4,8 @@ import (
 	"blocklist/internal/models"
 	"blocklist/internal/repository"
 	"context"
-	"github.com/bytedance/sonic"
 	"fmt"
+	"github.com/bytedance/sonic"
 	"io"
 	"net/http"
 	"net/netip"
diff --git a/internal/service/ip_service.go b/internal/service/ip_service.go
index 6be961f..1bd7475 100644
--- a/internal/service/ip_service.go
+++ b/internal/service/ip_service.go
@@ -2,8 +2,8 @@ package service
 
 import (
 	"context"
-	"github.com/bytedance/sonic"
 	"fmt"
+	"github.com/bytedance/sonic"
 	"html"
 	"net"
 	"net/netip"
@@ -1165,6 +1165,7 @@ type filterOptions struct {
 	fromTime     time.Time
 	toTime       time.Time
 }
+
 func (s *IPService) prepareFilterOptions(query, country, addedBy, from, to string) *filterOptions {
 	opts := &filterOptions{}
 	if from != "" {