diff --git a/.github/workflows/dependency-review.yml b/.github/workflows/dependency-review.yml
index 955b3b3fb..21a469b13 100644
--- a/.github/workflows/dependency-review.yml
+++ b/.github/workflows/dependency-review.yml
@@ -17,11 +17,11 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@91182cccc01eb5e619899d80e4e971d6181294a7 # v2.10.1
+        uses: step-security/harden-runner@0080882f6c36860b6ba35c610c98ce87d4e2f26f # v2.10.2
         with:
           egress-policy: audit
 
       - name: 'Checkout Repository'
         uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
       - name: 'Dependency Review'
-        uses: actions/dependency-review-action@4081bf99e2866ebe428fc0477b69eb4fcda7220a # v4.4.0
+        uses: actions/dependency-review-action@3b139cfc5fae8b618d3eae3675e383bb1769c019 # v4.5.0
diff --git a/.github/workflows/fuzzing.yml b/.github/workflows/fuzzing.yml
index af13aa801..385ccc75d 100644
--- a/.github/workflows/fuzzing.yml
+++ b/.github/workflows/fuzzing.yml
@@ -31,7 +31,7 @@ jobs:
 
     steps:
     - name: Harden Runner
-      uses: step-security/harden-runner@91182cccc01eb5e619899d80e4e971d6181294a7 # v2.10.1
+      uses: step-security/harden-runner@0080882f6c36860b6ba35c610c98ce87d4e2f26f # v2.10.2
       with:
         egress-policy: audit
 
@@ -44,7 +44,7 @@ jobs:
       run: echo "VALUE=platform-${{ matrix.platform }}_arch=${{ matrix.arch }}_type=fuzzing" >> $GITHUB_OUTPUT
 
     - name: Update the cache (ccache)
-      uses: actions/cache@6849a6489940f00c2f30c0fb92c6274307ccb58a # v4.1.2
+      uses: actions/cache@1bd1e32a3bdc45362d1e726936510720a7c30a57 # v4.2.0
       with:
         path: ccache
         key: ${{ steps.cache_key.outputs.VALUE }}_ccache
@@ -135,7 +135,7 @@ jobs:
 
     steps:
     - name: Harden Runner
-      uses: step-security/harden-runner@91182cccc01eb5e619899d80e4e971d6181294a7 # v2.10.1
+      uses: step-security/harden-runner@0080882f6c36860b6ba35c610c98ce87d4e2f26f # v2.10.2
       with:
         egress-policy: audit
 
@@ -144,7 +144,7 @@ jobs:
         submodules: 'recursive'
 
     - name: Cache the build folder
-      uses: actions/cache@6849a6489940f00c2f30c0fb92c6274307ccb58a
+      uses: actions/cache@1bd1e32a3bdc45362d1e726936510720a7c30a57
       env:
         cache-name: cache-nuget-modules
       with:
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 1f7c90928..7617da335 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -368,7 +368,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: Harden Runner
-      uses: step-security/harden-runner@91182cccc01eb5e619899d80e4e971d6181294a7 # v2.10.1
+      uses: step-security/harden-runner@0080882f6c36860b6ba35c610c98ce87d4e2f26f # v2.10.2
       with:
         egress-policy: audit
 
diff --git a/.github/workflows/posix.yml b/.github/workflows/posix.yml
index edc1453ab..aef34dba2 100644
--- a/.github/workflows/posix.yml
+++ b/.github/workflows/posix.yml
@@ -61,7 +61,7 @@ jobs:
 
     steps:
     - name: Harden Runner
-      uses: step-security/harden-runner@91182cccc01eb5e619899d80e4e971d6181294a7 # v2.10.1
+      uses: step-security/harden-runner@0080882f6c36860b6ba35c610c98ce87d4e2f26f # v2.10.2
       with:
         egress-policy: audit
 
@@ -71,7 +71,7 @@ jobs:
 
     - name: Initialize CodeQL
       if: inputs.build_codeql == true
-      uses: github/codeql-action/init@ea9e4e37992a54ee68a9622e985e60c8e8f12d9f
+      uses: github/codeql-action/init@df409f7d9260372bd5f19e5b04e83cb3c43714ae
       with:
         languages: 'cpp'
 
@@ -80,7 +80,7 @@ jobs:
       run: echo "VALUE=platform-${{ inputs.platform }}_arch=${{ inputs.arch }}_type-${{ inputs.build_type }}_sanitizers-${{ inputs.enable_sanitizers }}_coverage-${{ inputs.enable_coverage }}_scan_build-${{ inputs.scan_build }}_retpolines-${{ inputs.disable_retpolines }}" >> $GITHUB_OUTPUT
 
     - name: Update the cache (ccache)
-      uses: actions/cache@6849a6489940f00c2f30c0fb92c6274307ccb58a # v4.1.2
+      uses: actions/cache@1bd1e32a3bdc45362d1e726936510720a7c30a57 # v4.2.0
       with:
         path: ccache
         key: ${{ steps.cache_key.outputs.VALUE }}_ccache
@@ -306,4 +306,4 @@ jobs:
 
     - name: Perform CodeQL Analysis
       if: inputs.build_codeql == true
-      uses: github/codeql-action/analyze@ea9e4e37992a54ee68a9622e985e60c8e8f12d9f
+      uses: github/codeql-action/analyze@df409f7d9260372bd5f19e5b04e83cb3c43714ae
diff --git a/.github/workflows/scorecards.yml b/.github/workflows/scorecards.yml
index 4d9dd71b7..35656465b 100644
--- a/.github/workflows/scorecards.yml
+++ b/.github/workflows/scorecards.yml
@@ -31,7 +31,7 @@ jobs:
 
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@91182cccc01eb5e619899d80e4e971d6181294a7 # v2.10.1
+        uses: step-security/harden-runner@0080882f6c36860b6ba35c610c98ce87d4e2f26f # v2.10.2
         with:
           egress-policy: audit
 
@@ -71,6 +71,6 @@ jobs:
 
       # Upload the results to GitHub's code scanning dashboard.
       - name: "Upload to code-scanning"
-        uses: github/codeql-action/upload-sarif@ea9e4e37992a54ee68a9622e985e60c8e8f12d9f # v3.27.4
+        uses: github/codeql-action/upload-sarif@df409f7d9260372bd5f19e5b04e83cb3c43714ae # v3.27.9
         with:
           sarif_file: results.sarif
diff --git a/.github/workflows/update-docs.yml b/.github/workflows/update-docs.yml
index 62b6d060e..9e87b0567 100644
--- a/.github/workflows/update-docs.yml
+++ b/.github/workflows/update-docs.yml
@@ -30,7 +30,7 @@ jobs:
     steps:
 
     - name: Harden Runner
-      uses: step-security/harden-runner@91182cccc01eb5e619899d80e4e971d6181294a7
+      uses: step-security/harden-runner@0080882f6c36860b6ba35c610c98ce87d4e2f26f
       with:
         egress-policy: audit # TODO: change to 'egress-policy: block' after couple of runs
 
diff --git a/.github/workflows/windows.yml b/.github/workflows/windows.yml
index 86d92d0b5..9738f7ae5 100644
--- a/.github/workflows/windows.yml
+++ b/.github/workflows/windows.yml
@@ -47,7 +47,7 @@ jobs:
 
     steps:
     - name: Harden Runner
-      uses: step-security/harden-runner@91182cccc01eb5e619899d80e4e971d6181294a7 # v2.10.1
+      uses: step-security/harden-runner@0080882f6c36860b6ba35c610c98ce87d4e2f26f # v2.10.2
       with:
         egress-policy: audit
 
@@ -57,12 +57,12 @@ jobs:
 
     - name: Initialize CodeQL
       if: inputs.build_codeql == true
-      uses: github/codeql-action/init@ea9e4e37992a54ee68a9622e985e60c8e8f12d9f
+      uses: github/codeql-action/init@df409f7d9260372bd5f19e5b04e83cb3c43714ae
       with:
         languages: 'cpp'
 
     - name: Cache the build folder
-      uses: actions/cache@6849a6489940f00c2f30c0fb92c6274307ccb58a
+      uses: actions/cache@1bd1e32a3bdc45362d1e726936510720a7c30a57
       env:
         cache-name: cache-nuget-modules
       with:
@@ -124,4 +124,4 @@ jobs:
 
     - name: Perform CodeQL Analysis
       if: inputs.build_codeql == true
-      uses: github/codeql-action/analyze@ea9e4e37992a54ee68a9622e985e60c8e8f12d9f
+      uses: github/codeql-action/analyze@df409f7d9260372bd5f19e5b04e83cb3c43714ae
diff --git a/.gitignore b/.gitignore
index 672fbe7f2..2222dedae 100644
--- a/.gitignore
+++ b/.gitignore
@@ -9,6 +9,7 @@ __pycache__/
 # Distribution / packaging
 .Python
 build/
+build_fuzzer/
 develop-eggs/
 dist/
 downloads/
diff --git a/custom_tests/data/ubpf_test_atomic_validate.input b/custom_tests/data/ubpf_test_atomic_validate.input
new file mode 100644
index 000000000..8c23fd667
--- /dev/null
+++ b/custom_tests/data/ubpf_test_atomic_validate.input
@@ -0,0 +1 @@
+b4  00  00  00  00  00  00  00 db  01  00  00  42  00  00  00 95  00  00  00  00  00  00  00 
diff --git a/custom_tests/descrs/ubpf_test_atomic_validate.md b/custom_tests/descrs/ubpf_test_atomic_validate.md
new file mode 100644
index 000000000..27ecb3834
--- /dev/null
+++ b/custom_tests/descrs/ubpf_test_atomic_validate.md
@@ -0,0 +1,3 @@
+## Test Description
+
+This test verifies that the check for to validate an instruction properly handles the case where an atomic operation's immediate field does not contain a valid operation (according to Table 11 in the [spec](https://www.ietf.org/archive/id/draft-thaler-bpf-isa-00.html).
\ No newline at end of file
diff --git a/custom_tests/srcs/ubpf_test_atomic_validate.cc b/custom_tests/srcs/ubpf_test_atomic_validate.cc
new file mode 100644
index 000000000..ab9bd5a19
--- /dev/null
+++ b/custom_tests/srcs/ubpf_test_atomic_validate.cc
@@ -0,0 +1,51 @@
+// Copyright (c) Will Hawkins
+// SPDX-License-Identifier: Apache-2.0
+
+#include <cstdint>
+#include <iostream>
+#include <memory>
+#include <stdint.h>
+#include <string>
+
+extern "C"
+{
+#include "ubpf.h"
+}
+
+#include "ubpf_custom_test_support.h"
+
+int
+main(int argc, char** argv)
+{
+    std::string program_string{};
+    std::string error{};
+    ubpf_jit_fn jit_fn;
+
+    if (!get_program_string(argc, argv, program_string, error)) {
+        std::cerr << error << std::endl;
+        return 1;
+    }
+
+    uint64_t memory_expected{0x123456789};
+    uint64_t memory{0x123456789};
+
+    std::unique_ptr<ubpf_vm, decltype(&ubpf_destroy)> vm(ubpf_create(), ubpf_destroy);
+    if (!ubpf_setup_custom_test(
+            vm, program_string, [](ubpf_vm_up&, std::string&) { return true; }, jit_fn, error)) {
+        if (error == "Failed to load program: Invalid immediate value 66 for opcode DB.") {
+            return 0;
+        }
+
+        return 1;
+    }
+
+    return 1;
+
+    uint64_t bpf_return_value;
+    if (ubpf_exec(vm.get(), &memory, sizeof(memory), &bpf_return_value)) {
+        std::cerr << "Problem executing program" << std::endl;
+        return 1;
+    }
+
+    return !(memory == memory_expected);
+}
diff --git a/external/bpf_conformance b/external/bpf_conformance
index afc0282f7..514fa974b 160000
--- a/external/bpf_conformance
+++ b/external/bpf_conformance
@@ -1 +1 @@
-Subproject commit afc0282f775ce3f94b98b73498b9d4f77b1f2ff7
+Subproject commit 514fa974bdf0274a1365a2c4e738b5fe5b23cb75
diff --git a/vm/ubpf_instruction_valid.c b/vm/ubpf_instruction_valid.c
index c99480caa..07d2804bb 100644
--- a/vm/ubpf_instruction_valid.c
+++ b/vm/ubpf_instruction_valid.c
@@ -9,18 +9,32 @@
  * @brief Structure to filter valid fields for each eBPF instruction.
  * Default values are all zeros, which means the field is reserved and must be zero.
  */
-typedef struct _ubpf_inst_filter {
-    uint8_t opcode; ///< The opcode of the instruction.
-    uint8_t source_lower_bound; ///< The lower bound of the source register.
-    uint8_t source_upper_bound; ///< The upper bound of the source register.
-    uint8_t destination_lower_bound; ///< The lower bound of the destination register.
-    uint8_t destination_upper_bound; ///< The upper bound of the destination register.
-    int16_t offset_lower_bound; ///< The lower bound of the offset.
-    int16_t offset_upper_bound; ///< The upper bound of the offset.
-    int32_t immediate_lower_bound; ///< The lower bound of the immediate value.
-    int32_t immediate_upper_bound; ///< The upper bound of the immediate value.
+typedef struct _ubpf_inst_filter
+{
+    uint8_t opcode;                       ///< The opcode of the instruction.
+    uint8_t source_lower_bound;           ///< The lower bound of the source register.
+    uint8_t source_upper_bound;           ///< The upper bound of the source register.
+    uint8_t destination_lower_bound;      ///< The lower bound of the destination register.
+    uint8_t destination_upper_bound;      ///< The upper bound of the destination register.
+    int16_t offset_lower_bound;           ///< The lower bound of the offset.
+    int16_t offset_upper_bound;           ///< The upper bound of the offset.
+    int32_t immediate_lower_bound;        ///< The lower bound of the immediate value.
+    int32_t immediate_upper_bound;        ///< The upper bound of the immediate value.
+    int32_t* immediate_enumerated;        ///< A specific enumeration of the valid immediate values.
+    uint32_t immediate_enumerated_length; ///< The number of valid enumerated immediate values.
 } ubpf_inst_filter_t;
 
+static int32_t ebpf_atomic_store_immediate_enumerated[] = {
+    EBPF_ALU_OP_ADD,
+    EBPF_ALU_OP_ADD | EBPF_ATOMIC_OP_FETCH,
+    EBPF_ALU_OP_OR,
+    EBPF_ALU_OP_OR | EBPF_ATOMIC_OP_FETCH,
+    EBPF_ALU_OP_AND,
+    EBPF_ALU_OP_AND | EBPF_ATOMIC_OP_FETCH,
+    EBPF_ALU_OP_XOR,
+    EBPF_ALU_OP_XOR | EBPF_ATOMIC_OP_FETCH,
+    EBPF_ATOMIC_OP_XCHG | EBPF_ATOMIC_OP_FETCH,
+    EBPF_ATOMIC_OP_CMPXCHG | EBPF_ATOMIC_OP_FETCH};
 
 /**
  * @brief Array of valid eBPF instructions and their fields.
@@ -208,6 +222,7 @@ static ubpf_inst_filter_t _ubpf_instruction_filter[] = {
         .opcode = EBPF_OP_LE,
         .destination_lower_bound = BPF_REG_0,
         .destination_upper_bound = BPF_REG_9,
+        // specific valid values for the immediate field are checked in validate.
         .immediate_lower_bound = 0,
         .immediate_upper_bound = 64,
     },
@@ -215,6 +230,7 @@ static ubpf_inst_filter_t _ubpf_instruction_filter[] = {
         .opcode = EBPF_OP_BE,
         .destination_lower_bound = BPF_REG_0,
         .destination_upper_bound = BPF_REG_9,
+        // specific valid values for the immediate field are checked in validate.
         .immediate_lower_bound = 0,
         .immediate_upper_bound = 64,
     },
@@ -503,6 +519,9 @@ static ubpf_inst_filter_t _ubpf_instruction_filter[] = {
         .opcode = EBPF_OP_LDDW,
         .destination_lower_bound = BPF_REG_0,
         .destination_upper_bound = BPF_REG_10,
+        // specific valid source values are checked in validate.
+        .source_lower_bound = 0,
+        .source_upper_bound = 6,
         .immediate_lower_bound = INT32_MIN,
         .immediate_upper_bound = INT32_MAX,
     },
@@ -934,8 +953,8 @@ static ubpf_inst_filter_t _ubpf_instruction_filter[] = {
         .destination_upper_bound = BPF_REG_10,
         .source_lower_bound = BPF_REG_0,
         .source_upper_bound = BPF_REG_10,
-        .immediate_lower_bound = 0x0,
-        .immediate_upper_bound = 0xff,
+        .immediate_enumerated = ebpf_atomic_store_immediate_enumerated,
+        .immediate_enumerated_length = 10,
         .offset_lower_bound = INT16_MIN,
         .offset_upper_bound = INT16_MAX,
     },
@@ -994,10 +1013,25 @@ ubpf_is_valid_instruction(const struct ebpf_inst insts, char ** errmsg)
         return false;
     }
 
-    // Validate immediate value.
-    if (!_in_range(insts.imm, filter->immediate_lower_bound, filter->immediate_upper_bound)) {
-        *errmsg = ubpf_error("Invalid immediate value %d for opcode %2X.", insts.imm, insts.opcode);
-        return false;
+    // Validate immediate values in the presence of enumerated values.
+    if (filter->immediate_enumerated != NULL) {
+        bool valid = false;
+        for (int i = 0; i < filter->immediate_enumerated_length; i++) {
+            if (filter->immediate_enumerated[i] == insts.imm) {
+                valid = true;
+                break;
+            }
+        }
+        if (!valid) {
+            *errmsg = ubpf_error("Invalid immediate value %d for opcode %2X.", insts.imm, insts.opcode);
+            return false;
+        }
+    } else {
+        // Validate immediate value.
+        if (!_in_range(insts.imm, filter->immediate_lower_bound, filter->immediate_upper_bound)) {
+            *errmsg = ubpf_error("Invalid immediate value %d for opcode %2X.", insts.imm, insts.opcode);
+            return false;
+        }
     }
 
     // Validate offset value.