diff --git a/maven-resolver-impl/src/main/java/org/eclipse/aether/internal/impl/LocalPathPrefixComposerFactorySupport.java b/maven-resolver-impl/src/main/java/org/eclipse/aether/internal/impl/LocalPathPrefixComposerFactorySupport.java
index a01b377c83..6d320c9f3a 100644
--- a/maven-resolver-impl/src/main/java/org/eclipse/aether/internal/impl/LocalPathPrefixComposerFactorySupport.java
+++ b/maven-resolver-impl/src/main/java/org/eclipse/aether/internal/impl/LocalPathPrefixComposerFactorySupport.java
@@ -24,6 +24,7 @@
 import org.eclipse.aether.repository.RemoteRepository;
 import org.eclipse.aether.repository.RepositoryKeyFunction;
 import org.eclipse.aether.util.ConfigUtils;
+import org.eclipse.aether.util.PathUtils;
 
 /**
  * Support class for {@link LocalPathPrefixComposerFactory} implementations: it predefines and makes re-usable
@@ -286,13 +287,13 @@ public String getPathPrefixForRemoteArtifact(Artifact artifact, RemoteRepository
             }
             String result = remotePrefix;
             if (!splitRemoteRepositoryLast && splitRemoteRepository) {
-                result += "/" + repositoryKeyFunction.apply(repository, null);
+                result += "/" + repositoryKeySegment(repository);
             }
             if (splitRemote) {
                 result += "/" + (artifact.isSnapshot() ? snapshotsPrefix : releasesPrefix);
             }
             if (splitRemoteRepositoryLast && splitRemoteRepository) {
-                result += "/" + repositoryKeyFunction.apply(repository, null);
+                result += "/" + repositoryKeySegment(repository);
             }
             return result;
         }
@@ -316,13 +317,13 @@ public String getPathPrefixForRemoteMetadata(Metadata metadata, RemoteRepository
             }
             String result = remotePrefix;
             if (!splitRemoteRepositoryLast && splitRemoteRepository) {
-                result += "/" + repositoryKeyFunction.apply(repository, null);
+                result += "/" + repositoryKeySegment(repository);
             }
             if (splitRemote) {
                 result += "/" + (isSnapshot(metadata) ? snapshotsPrefix : releasesPrefix);
             }
             if (splitRemoteRepositoryLast && splitRemoteRepository) {
-                result += "/" + repositoryKeyFunction.apply(repository, null);
+                result += "/" + repositoryKeySegment(repository);
             }
             return result;
         }
@@ -330,5 +331,15 @@ public String getPathPrefixForRemoteMetadata(Metadata metadata, RemoteRepository
         protected boolean isSnapshot(Metadata metadata) {
             return !metadata.getVersion().isEmpty() && metadata.getVersion().endsWith("-SNAPSHOT");
         }
+
+        /**
+         * Defense in depth: the repository key is spliced into the local repository path prefix, so it
+         * must be a safe path segment.
+         */
+        private String repositoryKeySegment(RemoteRepository repository) {
+            String key = repositoryKeyFunction.apply(repository, null);
+            PathUtils.validatePathComponent(key, "repository key");
+            return key;
+        }
     }
 }
diff --git a/maven-resolver-impl/src/main/java/org/eclipse/aether/internal/impl/checksum/SparseDirectoryTrustedChecksumsSource.java b/maven-resolver-impl/src/main/java/org/eclipse/aether/internal/impl/checksum/SparseDirectoryTrustedChecksumsSource.java
index 0456b3f179..8094374ca1 100644
--- a/maven-resolver-impl/src/main/java/org/eclipse/aether/internal/impl/checksum/SparseDirectoryTrustedChecksumsSource.java
+++ b/maven-resolver-impl/src/main/java/org/eclipse/aether/internal/impl/checksum/SparseDirectoryTrustedChecksumsSource.java
@@ -39,6 +39,7 @@
 import org.eclipse.aether.spi.io.ChecksumProcessor;
 import org.eclipse.aether.spi.remoterepo.RepositoryKeyFunctionFactory;
 import org.eclipse.aether.util.ConfigUtils;
+import org.eclipse.aether.util.PathUtils;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -178,6 +179,9 @@ private String calculateArtifactPath(
         String path = localPathComposer.getPathForArtifact(artifact, false) + "."
                 + checksumAlgorithmFactory.getFileExtension();
         if (originAware) {
+            // defense in depth: the repository key is spliced into a path under the checksums basedir,
+            // so it must be a safe path segment
+            PathUtils.validatePathComponent(safeRepositoryId, "repository key");
             path = safeRepositoryId + "/" + path;
         }
         return path;
diff --git a/maven-resolver-impl/src/test/java/org/eclipse/aether/internal/impl/DefaultLocalPathPrefixComposerFactoryTest.java b/maven-resolver-impl/src/test/java/org/eclipse/aether/internal/impl/DefaultLocalPathPrefixComposerFactoryTest.java
index 8f6c53452f..a0ecc3c696 100644
--- a/maven-resolver-impl/src/test/java/org/eclipse/aether/internal/impl/DefaultLocalPathPrefixComposerFactoryTest.java
+++ b/maven-resolver-impl/src/test/java/org/eclipse/aether/internal/impl/DefaultLocalPathPrefixComposerFactoryTest.java
@@ -232,4 +232,30 @@ void fullConfig() {
         assertNotNull(prefix);
         assertEquals("cached/my-repo/releases", prefix);
     }
+
+    @Test
+    void dotDotRepositoryIdIsNeutralizedInSplitPrefix() {
+        DefaultRepositorySystemSession session = TestUtils.newSession();
+        session.setConfigProperty(DefaultLocalPathPrefixComposerFactory.CONFIG_PROP_SPLIT, Boolean.TRUE.toString());
+        session.setConfigProperty(
+                DefaultLocalPathPrefixComposerFactory.CONFIG_PROP_SPLIT_REMOTE_REPOSITORY, Boolean.TRUE.toString());
+
+        LocalPathPrefixComposerFactory factory =
+                new DefaultLocalPathPrefixComposerFactory(new DefaultRepositoryKeyFunctionFactory());
+        LocalPathPrefixComposer composer = factory.createComposer(session);
+        assertNotNull(composer);
+
+        // a repository id of ".." must be neutralized into a harmless path segment rather than spliced
+        // into the prefix as-is
+        RemoteRepository dotDotRepository =
+                new RemoteRepository.Builder("..", "default", "https://repo.example.org/").build();
+
+        String prefix = composer.getPathPrefixForRemoteArtifact(releaseArtifact, dotDotRepository);
+        assertNotNull(prefix);
+        assertEquals("cached/-DOTDOT-", prefix);
+
+        prefix = composer.getPathPrefixForRemoteMetadata(releaseMetadata, dotDotRepository);
+        assertNotNull(prefix);
+        assertEquals("cached/-DOTDOT-", prefix);
+    }
 }
diff --git a/maven-resolver-util/src/main/java/org/eclipse/aether/util/PathUtils.java b/maven-resolver-util/src/main/java/org/eclipse/aether/util/PathUtils.java
index b853ae1113..f44c28b38a 100644
--- a/maven-resolver-util/src/main/java/org/eclipse/aether/util/PathUtils.java
+++ b/maven-resolver-util/src/main/java/org/eclipse/aether/util/PathUtils.java
@@ -73,7 +73,16 @@ public static String stringToPathSegment(String string) {
                 pos = result.indexOf(illegal);
             }
         }
-        return result.toString();
+        // Strings consisting solely of dots contain no illegal character, yet "." and ".." carry path
+        // meaning when used as a path segment. Map them to explicit tokens, mirroring the character
+        // replacements above.
+        String segment = result.toString();
+        if (segment.equals(".")) {
+            return "-DOT-";
+        } else if (segment.equals("..")) {
+            return "-DOTDOT-";
+        }
+        return segment;
     }
 
     /**
diff --git a/maven-resolver-util/src/test/java/org/eclipse/aether/util/PathUtilsTest.java b/maven-resolver-util/src/test/java/org/eclipse/aether/util/PathUtilsTest.java
index 97c1b45631..a38d4ef935 100644
--- a/maven-resolver-util/src/test/java/org/eclipse/aether/util/PathUtilsTest.java
+++ b/maven-resolver-util/src/test/java/org/eclipse/aether/util/PathUtilsTest.java
@@ -40,6 +40,18 @@ void stringToPathSegment_fixes() {
         assertEquals("bad-COLON-id", badFixedId);
     }
 
+    @Test
+    void stringToPathSegment_dotSegments() {
+        // "." and ".." contain no illegal character, but carry path meaning when used as a path segment
+        assertEquals("-DOTDOT-", PathUtils.stringToPathSegment(".."));
+        assertEquals("-DOT-", PathUtils.stringToPathSegment("."));
+        // dotted names and longer dot runs are inert as single path segments and stay untouched
+        assertEquals("...", PathUtils.stringToPathSegment("..."));
+        assertEquals("my.repo", PathUtils.stringToPathSegment("my.repo"));
+        assertEquals("repo..id", PathUtils.stringToPathSegment("repo..id"));
+        assertEquals("..id", PathUtils.stringToPathSegment("..id"));
+    }
+
     @Test
     void stringToPathSegment_allCharsBad() {
         String veryBad = "\\/:\"<>|?*";