Medium· 4.3GHSA-463r-5m89-4xfr CVE-2026-53437CWE-601Published Jun 10, 2026

Jenkins Open Redirect Through Newline/Tab Characters in Redirect URL

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Affected versions

0 → fixed in 2.555.32.556 → fixed in 2.568

Details

Jenkins 2.567 and earlier, LTS 2.555.2 and earlier improperly determines that a redirect URL after login is legitimately pointing to Jenkins when it contains tab or newline characters between `//`, allowing attackers to perform phishing attacks.

The fix

[SECURITY-3711][SECURITY-3755]

Kevin-CB· May 29, 2026, 07:39 AM+32−9b32f2f27a8

core/src/main/java/hudson/Util.java+3 −2

@@ -1647,11 +1647,12 @@ public static boolean isAbsoluteUri(@NonNull String uri) {
     }
  
     /**
-     * Return true iff the parameter does not denote an absolute URI and not a scheme-relative URI.
+     * Return true if and only if the parameter does not denote an absolute URI and not a scheme-relative URI.
      * @since 2.3 / 1.651.2
      */
     public static boolean isSafeToRedirectTo(@NonNull String uri) {
-        return !isAbsoluteUri(uri) && !uri.startsWith("\\") && !uri.replace('\\', '/').startsWith("//");
+        String normalized = uri.replace("\t", "").replace("\n", "").replace("\r", "");
+        return !isAbsoluteUri(normalized) && !normalized.startsWith("\\") && !normalized.replace('\\', '/').contains("//");
     }
  
     /**

core/src/test/java/hudson/UtilTest.java+14 −1

@@ -415,7 +415,7 @@ void testIsAbsoluteUri() {
     }
  
     @Test
-    @Issue({"SECURITY-276", "SECURITY-3501"})
+    @Issue({"SECURITY-276", "SECURITY-3501", "SECURITY-3711"})
     void testIsSafeToRedirectTo() {
         assertFalse(Util.isSafeToRedirectTo("http://foobar/"));
         assertFalse(Util.isSafeToRedirectTo("mailto:kk@kohsuke.org"));
@@ -426,6 +426,19 @@ void testIsSafeToRedirectTo() {
         assertFalse(Util.isSafeToRedirectTo("/\\google.com"));
         assertFalse(Util.isSafeToRedirectTo("\\google.com"));
  
+        assertFalse(Util.isSafeToRedirectTo(".//google.com"));
+        assertFalse(Util.isSafeToRedirectTo(".///google.com"));
+        assertFalse(Util.isSafeToRedirectTo("aaa/..//google.com"));
+        assertFalse(Util.isSafeToRedirectTo("./aaa/..//google.com"));
+        assertFalse(Util.isSafeToRedirectTo("./\\/google.com"));
+ 
+        assertFalse(Util.isSafeToRedirectTo("/\t/google.com"));
+        assertFalse(Util.isSafeToRedirectTo("/\n/google.com"));
+        assertFalse(Util.isSafeToRedirectTo("/\r/google.com"));
+        assertFalse(Util.isSafeToRedirectTo("\t//google.com"));
+        assertFalse(Util.isSafeToRedirectTo("/\t/\t/google.com"));
+        assertFalse(Util.isSafeToRedirectTo("/\t\n\r/google.com"));
+ 
         assertTrue(Util.isSafeToRedirectTo("foo/bar/abc:def"));
         assertTrue(Util.isSafeToRedirectTo("foo?abc:def"));
         assertTrue(Util.isSafeToRedirectTo("foo#abc:def"));

test/src/test/java/jenkins/security/Security3501Test.java+15 −6

@@ -13,6 +13,7 @@
 import org.junit.jupiter.params.Parameter;
 import org.junit.jupiter.params.ParameterizedClass;
 import org.junit.jupiter.params.provider.ValueSource;
+import org.jvnet.hudson.test.Issue;
 import org.jvnet.hudson.test.JenkinsRule;
 import org.jvnet.hudson.test.junit.jupiter.RealJenkinsExtension;
  
@@ -31,6 +32,7 @@ void setUp() {
         jj.withPrefix(contextPath);
     }
  
+    @Issue({"SECURITY-3501", "SECURITY-3711"})
     @Test
     void testRedirects() throws Throwable {
         jj.then(new TestRedirectsStep(contextPath));
@@ -38,20 +40,27 @@ void testRedirects() throws Throwable {
  
     private record TestRedirectsStep(String context) implements RealJenkinsExtension.Step {
         public void run(JenkinsRule j) throws Exception {
-            List<String> prohibitedPaths = List.of("%5C%5Cexample.org", "%5C/example.org", "/%5Cexample.org", "//example.org", "https://example.org", "\\example.org");
+            List<String> prohibitedPaths = List.of(
+                    // SECURITY-3501
+                    "%5C%5Cexample.org", "%5C/example.org", "/%5Cexample.org", "//example.org",
+                    "https://example.org", "\\example.org",
+                    ".//example.org", ".///example.org", ".////example.org",
+                    "aaa/..//example.org", "./aaa/..//example.org", "./%5C/example.org",
+                    "/%09/example.org", "/%0A/example.org", "/%0D/example.org",
+                    "%09//example.org", "/%09/%09/example.org");
             for (String path : prohibitedPaths) {
                 try (JenkinsRule.WebClient wc = j.createWebClient().withRedirectEnabled(false)) {
-                    final FailingHttpStatusCodeException fhsce = assertThrows(FailingHttpStatusCodeException.class, () -> wc.goTo("redirects/content?path=" + path));
-                    assertThat(fhsce.getStatusCode(), is(404));
+                    final FailingHttpStatusCodeException fhsce = assertThrows(FailingHttpStatusCodeException.class, () -> wc.goTo("redirects/content?path=" + path), "path=" + path);
+                    assertThat("path=" + path, fhsce.getStatusCode(), is(404));
                 }
             }
  
             List<String> allowedPaths = List.of("foo", "foo/bar");
             for (String path : allowedPaths) {
                 try (JenkinsRule.WebClient wc = j.createWebClient().withRedirectEnabled(false)) {
-                    final FailingHttpStatusCodeException fhsce = assertThrows(FailingHttpStatusCodeException.class, () -> wc.goTo("redirects/content?path=" + path));
-                    assertThat(fhsce.getStatusCode(), is(302));
-                    assertThat(fhsce.getResponse().getResponseHeaderValue("Location"), is(context + "/redirects/" + path));
+                    final FailingHttpStatusCodeException fhsce = assertThrows(FailingHttpStatusCodeException.class, () -> wc.goTo("redirects/content?path=" + path), "path=" + path);
+                    assertThat("path=" + path, fhsce.getStatusCode(), is(302));
+                    assertThat("path=" + path, fhsce.getResponse().getResponseHeaderValue("Location"), is(context + "/redirects/" + path));
                 }
             }
         }