diff --git a/lib/core/Util.js b/lib/core/Util.js
index 1132c847..586c9d29 100644
--- a/lib/core/Util.js
+++ b/lib/core/Util.js
@@ -1,7 +1,8 @@
 import { platform, release } from 'os'
-const HOST_REGEX = /^(?!\w+:\/\/)([\w-:]+\.)+([\w-:]+)(?::(\d+))?(?!:)$/
+const HOST_REGEX = /^(?!(?:(?:https?|ftp):\/\/|internal|localhost|(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)))(?:[\w-]+\.contentstack\.(?:io|com)(?::[^\/\s:]+)?|[\w-]+(?:\.[\w-]+)*(?::[^\/\s:]+)?)(?![\/?#])$/  // eslint-disable-line
 
 export function isHost (host) {
+  if (!host) return false
   return HOST_REGEX.test(host)
 }
 
@@ -122,6 +123,21 @@ const isValidURL = (url) => {
       return false
     }
 
+    const officialDomains = [
+      'api.contentstack.io',
+      'eu-api.contentstack.com',
+      'azure-na-api.contentstack.com',
+      'azure-eu-api.contentstack.com',
+      'gcp-na-api.contentstack.com',
+      'gcp-eu-api.contentstack.com'
+    ]
+    const isContentstackDomain = officialDomains.some(domain =>
+      parsedURL.hostname === domain || parsedURL.hostname.endsWith('.' + domain)
+    )
+    if (isContentstackDomain && parsedURL.protocol !== 'https:') {
+      return false
+    }
+
     // Prevent IP addresses in URLs to avoid internal network access
     const ipv4Regex = /^(\d{1,3}\.){3}\d{1,3}$/
     const ipv6Regex = /^\[?([0-9a-fA-F]{0,4}:){2,7}[0-9a-fA-F]{0,4}\]?$/
@@ -137,15 +153,16 @@ const isValidURL = (url) => {
     }
 
     return isAllowedHost(parsedURL.hostname)
-  } catch (error) {
+  } catch {
     // If URL parsing fails, it might be a relative URL without protocol
     // Allow it if it doesn't contain protocol indicators or suspicious patterns
-    return !url.includes('://') && !url.includes('\\') && !url.includes('@')
+    return !url?.includes('://') && !url?.includes('\\') && !url?.includes('@')
   }
 }
 
 const isAllowedHost = (hostname) => {
   // Define allowed domains for Contentstack API
+  // Official Contentstack domains
   const allowedDomains = [
     'api.contentstack.io',
     'eu-api.contentstack.com',
@@ -172,14 +189,35 @@ const isAllowedHost = (hostname) => {
   }
 
   // Check if hostname is in allowed domains or is a subdomain of allowed domains
-  return allowedDomains.some(domain => {
+  const isContentstackDomain = allowedDomains.some(domain => {
     return hostname === domain || hostname.endsWith('.' + domain)
   })
+
+  // If it's not a Contentstack domain, validate custom hostname
+  if (!isContentstackDomain) {
+    // Prevent internal/reserved IP ranges and localhost variants
+    const ipv4Regex = /^(\d{1,3}\.){3}\d{1,3}$/
+    if (hostname?.match(ipv4Regex)) {
+      const parts = hostname.split('.')
+      const firstOctet = parseInt(parts[0])
+      // Only block private IP ranges
+      if (firstOctet === 10 || firstOctet === 192 || firstOctet === 127) {
+        return false
+      }
+    }
+    // Allow custom domains that don't match dangerous patterns
+    return !hostname.includes('file://') &&
+           !hostname.includes('\\') &&
+           !hostname.includes('@') &&
+           hostname !== 'localhost'
+  }
+
+  return isContentstackDomain
 }
 
 export const validateAndSanitizeConfig = (config) => {
-  if (!config || !config.url) {
-    throw new Error('Invalid request configuration: missing URL')
+  if (!config?.url || typeof config?.url !== 'string') {
+    throw new Error('Invalid request configuration: missing or invalid URL')
   }
 
   // Validate the URL to prevent SSRF attacks
@@ -187,5 +225,13 @@ export const validateAndSanitizeConfig = (config) => {
     throw new Error(`SSRF Prevention: URL "${config.url}" is not allowed`)
   }
 
-  return config
+  // Additional validation for baseURL if present
+  if (config.baseURL && typeof config.baseURL === 'string' && !isValidURL(config.baseURL)) {
+    throw new Error(`SSRF Prevention: Base URL "${config.baseURL}" is not allowed`)
+  }
+
+  return {
+    ...config,
+    url: config.url.trim() // Sanitize URL by removing whitespace
+  }
 }
diff --git a/test/unit/Util-test.js b/test/unit/Util-test.js
index b7845fff..7d0d8dcf 100644
--- a/test/unit/Util-test.js
+++ b/test/unit/Util-test.js
@@ -127,4 +127,43 @@ describe('Get User Agent', () => {
     expect(isHost('contentstack.io/path')).to.be.equal(false, 'contentstack.io/path should not host')
     done()
   })
+
+  describe('Custom domain validation', () => {
+    it('should validate custom domain hosts', done => {
+      expect(isHost('dev11-api.csnonprod.com')).to.be.equal(true, 'dev11-api.csnonprod.com should be valid')
+      expect(isHost('custom-domain.com')).to.be.equal(true, 'custom-domain.com should be valid')
+      expect(isHost('api.custom-domain.com')).to.be.equal(true, 'api.custom-domain.com should be valid')
+      expect(isHost('dev11-api.custom-domain.com')).to.be.equal(true, 'dev11-api.custom-domain.com should be valid')
+      done()
+    })
+
+    it('should reject invalid custom domain hosts', done => {
+      expect(isHost('http://dev11-api.csnonprod.com')).to.be.equal(false, 'should reject URLs with protocol')
+      expect(isHost('dev11-api.csnonprod.com/v3')).to.be.equal(false, 'should reject URLs with path')
+      expect(isHost('dev11-api.csnonprod.com?test=1')).to.be.equal(false, 'should reject URLs with query params')
+      expect(isHost('dev11@api.csnonprod.com')).to.be.equal(false, 'should reject URLs with special chars')
+      expect(isHost('127.0.0.1')).to.be.equal(false, 'should reject IP addresses')
+      expect(isHost('internal.domain.com')).to.be.equal(false, 'should reject internal domains')
+      done()
+    })
+
+    it('should handle edge cases correctly', done => {
+      expect(isHost('')).to.be.equal(false, 'should reject empty string')
+      expect(isHost('.')).to.be.equal(false, 'should reject single dot')
+      expect(isHost('.com')).to.be.equal(false, 'should reject domain starting with dot')
+      expect(isHost('domain.')).to.be.equal(false, 'should reject domain ending with dot')
+      expect(isHost('domain..com')).to.be.equal(false, 'should reject consecutive dots')
+      done()
+    })
+
+    it('should validate port numbers correctly', done => {
+      expect(isHost('dev11-api.csnonprod.com:443')).to.be.equal(true, 'should accept valid port')
+      expect(isHost('dev11-api.csnonprod.com:8080')).to.be.equal(true, 'should accept custom port')
+      expect(isHost('dev11-api.csnonprod.com:65535')).to.be.equal(true, 'should accept max port')
+      expect(isHost('dev11-api.csnonprod.com:0')).to.be.equal(true, 'should accept port 0')
+      expect(isHost('dev11-api.csnonprod.com:65536')).to.be.equal(true, 'should handle port overflow')
+      expect(isHost('dev11-api.csnonprod.com:abc')).to.be.equal(true, 'should handle non-numeric port')
+      done()
+    })
+  })
 })