diff --git a/.github/dependabot.yml b/.github/dependabot.yml
index 4dca3d3149..d230c95b3a 100644
--- a/.github/dependabot.yml
+++ b/.github/dependabot.yml
@@ -95,6 +95,11 @@ updates:
       # Shiro 2.x jars are already Java 11 bytecode; freeze automated bumps.
       - dependency-name: "org.apache.shiro*"
       - dependency-name: "org.apache.shiro:*"
+      # Bouncy Castle `jdk18on` 1.78+ is Java 11 bytecode; we pin the
+      # `jdk15to18` line via <bc.version> in the root pom (Java 5 bytecode).
+      # Block Dependabot from re-bundling the wrong artifact line.
+      - dependency-name: "org.bouncycastle*"
+      - dependency-name: "org.bouncycastle:*"
       # Jackrabbit 2.21+ is Java 11 (2.20.x is last Java 8 line we track).
       - dependency-name: "org.apache.jackrabbit*"
       - dependency-name: "org.apache.jackrabbit:*"
diff --git a/WebUI/pom.xml b/WebUI/pom.xml
index 6fec8b1582..187f289e24 100644
--- a/WebUI/pom.xml
+++ b/WebUI/pom.xml
@@ -434,23 +434,23 @@
         </dependency>
         <dependency>
             <groupId>org.bouncycastle</groupId>
-            <artifactId>bcmail-jdk18on</artifactId>
+            <artifactId>bcmail-jdk15to18</artifactId>
         </dependency>
         <dependency>
             <groupId>org.bouncycastle</groupId>
-            <artifactId>bcpg-jdk18on</artifactId>
+            <artifactId>bcpg-jdk15to18</artifactId>
         </dependency>
         <dependency>
             <groupId>org.bouncycastle</groupId>
-            <artifactId>bcpkix-jdk18on</artifactId>
+            <artifactId>bcpkix-jdk15to18</artifactId>
         </dependency>
         <dependency>
             <groupId>org.bouncycastle</groupId>
-            <artifactId>bcprov-jdk18on</artifactId>
+            <artifactId>bcprov-jdk15to18</artifactId>
         </dependency>
         <dependency>
             <groupId>org.bouncycastle</groupId>
-            <artifactId>bctls-jdk18on</artifactId>
+            <artifactId>bctls-jdk15to18</artifactId>
         </dependency>
         <dependency>
             <groupId>javax.servlet</groupId>
diff --git a/deliverytiersuite/delivery-tier-suite/common/pom.xml b/deliverytiersuite/delivery-tier-suite/common/pom.xml
index 74f5638960..1b24bdff95 100644
--- a/deliverytiersuite/delivery-tier-suite/common/pom.xml
+++ b/deliverytiersuite/delivery-tier-suite/common/pom.xml
@@ -150,7 +150,7 @@
         </dependency>
         <dependency>
             <groupId>org.bouncycastle</groupId>
-            <artifactId>bcprov-jdk18on</artifactId>
+            <artifactId>bcprov-jdk15to18</artifactId>
             <version>${bc.version}</version>
             <scope>compile</scope>
         </dependency>
diff --git a/modules/CMLight-Main-cactus-tests/pom.xml b/modules/CMLight-Main-cactus-tests/pom.xml
index 681cc99a1f..50fbb79c0d 100644
--- a/modules/CMLight-Main-cactus-tests/pom.xml
+++ b/modules/CMLight-Main-cactus-tests/pom.xml
@@ -281,15 +281,15 @@
                 </exclusion>
                 <exclusion>
                     <groupId>org.bouncycastle</groupId>
-                    <artifactId>bcmail-jdk18on</artifactId>
+                    <artifactId>bcmail-jdk15to18</artifactId>
                 </exclusion>
                 <exclusion>
                     <groupId>org.bouncycastle</groupId>
-                    <artifactId>bcprov-jdk18on</artifactId>
+                    <artifactId>bcprov-jdk15to18</artifactId>
                 </exclusion>
                 <exclusion>
                     <groupId>org.bouncycastle</groupId>
-                    <artifactId>bcpg-jdk18on</artifactId>
+                    <artifactId>bcpg-jdk15to18</artifactId>
                 </exclusion>
             </exclusions>
             <scope>test</scope>
diff --git a/modules/perc-security-utils/pom.xml b/modules/perc-security-utils/pom.xml
index 8538a38f9d..2f9f1b0c3e 100644
--- a/modules/perc-security-utils/pom.xml
+++ b/modules/perc-security-utils/pom.xml
@@ -54,7 +54,7 @@
         </dependency>
         <dependency>
             <groupId>org.bouncycastle</groupId>
-            <artifactId>bcprov-jdk18on</artifactId>
+            <artifactId>bcprov-jdk15to18</artifactId>
         </dependency>
         <dependency>
             <groupId>org.jasypt</groupId>
diff --git a/pom.xml b/pom.xml
index ecbdd3458e..6bb4b9583b 100644
--- a/pom.xml
+++ b/pom.xml
@@ -78,7 +78,7 @@
         <axis.version>1.4.1</axis.version>
         <axiscore.version>1.4.2</axiscore.version>
         <batik.version>1.19</batik.version>
-        <bc.version>1.83</bc.version>
+        <bc.version>1.85</bc.version>
         <build.helper.maven.plugin.version>3.6.1</build.helper.maven.plugin.version>
         <build.profile.id>dev</build.profile.id>
         <buildId>0</buildId>
@@ -1958,27 +1958,27 @@
             </dependency>
             <dependency>
                 <groupId>org.bouncycastle</groupId>
-                <artifactId>bcmail-jdk18on</artifactId>
+                <artifactId>bcmail-jdk15to18</artifactId>
                 <version>${bc.version}</version>
             </dependency>
             <dependency>
                 <groupId>org.bouncycastle</groupId>
-                <artifactId>bcpg-jdk18on</artifactId>
+                <artifactId>bcpg-jdk15to18</artifactId>
                 <version>${bc.version}</version>
             </dependency>
             <dependency>
                 <groupId>org.bouncycastle</groupId>
-                <artifactId>bcpkix-jdk18on</artifactId>
+                <artifactId>bcpkix-jdk15to18</artifactId>
                 <version>${bc.version}</version>
             </dependency>
             <dependency>
                 <groupId>org.bouncycastle</groupId>
-                <artifactId>bcprov-jdk18on</artifactId>
+                <artifactId>bcprov-jdk15to18</artifactId>
                 <version>${bc.version}</version>
             </dependency>
             <dependency>
                 <groupId>org.bouncycastle</groupId>
-                <artifactId>bctls-jdk18on</artifactId>
+                <artifactId>bctls-jdk15to18</artifactId>
                 <version>${bc.version}</version>
             </dependency>
             <dependency>
diff --git a/system/pom.xml b/system/pom.xml
index d400b74d87..d9a71d4442 100644
--- a/system/pom.xml
+++ b/system/pom.xml
@@ -906,19 +906,19 @@
         </dependency>
         <dependency>
             <groupId>org.bouncycastle</groupId>
-            <artifactId>bcprov-jdk18on</artifactId>
+            <artifactId>bcprov-jdk15to18</artifactId>
         </dependency>
         <dependency>
             <groupId>org.bouncycastle</groupId>
-            <artifactId>bctls-jdk18on</artifactId>
+            <artifactId>bctls-jdk15to18</artifactId>
         </dependency>
         <dependency>
             <groupId>org.bouncycastle</groupId>
-            <artifactId>bcpkix-jdk18on</artifactId>
+            <artifactId>bcpkix-jdk15to18</artifactId>
         </dependency>
         <dependency>
             <groupId>org.bouncycastle</groupId>
-            <artifactId>bcpg-jdk18on</artifactId>
+            <artifactId>bcpg-jdk15to18</artifactId>
         </dependency>
         <dependency>
             <groupId>com.amazonaws</groupId>