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Medium severity5.9NVD Advisory· Published Apr 30, 2026· Updated May 5, 2026

CVE-2026-32148

CVE-2026-32148

Description

Insufficient Verification of Data Authenticity vulnerability in hexpm hex (Hex.RemoteConverger module) allows dependency integrity bypass via unverified lockfile checksums.

Hex stores checksums for dependencies in the mix.lock file to ensure reproducible and integrity-checked builds. However, Hex.RemoteConverger.verify_resolved/2 never executes checksum verification because the lock data returned by Hex.Utils.lock/1 uses string-based dependency names, while the verification logic compares against atom-based names. This type mismatch causes the verification code path to be silently skipped. Checksums are still validated when packages are initially downloaded from the registry, but mismatches between the lockfile and resolved dependencies are not detected.

An attacker who can influence cached packages (e.g., via local cache poisoning or a compromised registry) can provide modified dependency contents that will be accepted without detection. The mix.lock file is silently rewritten with the checksum values from the registry, erasing evidence of tampering.

This issue affects hex: from 0.16.0 before 2.4.2.

Affected products

2
  • Hexpm/Hexreferences
  • Hex/Hex
    cpe:2.3:a:hex:hex:*:*:*:*:*:*:*:*
    Range: >=0.16.0,<2.4.2

Patches

1
d7528c8199a1

Fix checksum verification for dependencies in mix.lock

https://github.com/hexpm/hexEric Meadows-JönssonApr 30, 2026via nvd-ref
commit
2 files changed · +54 −4
  • lib/hex/remote_converger.ex+4 −4 modified
    @@ -569,10 +569,8 @@ defmodule Hex.RemoteConverger do
 
   defp verify_resolved(resolved, lock) do
     Enum.each(resolved, fn {repo, name, app, version} ->
-      atom_name = String.to_atom(name)
-
       case Hex.Utils.lock(lock[String.to_atom(app)]) do
-        %{name: ^atom_name, version: ^version, repo: ^repo} = lock ->
+        %{name: ^name, version: ^version, repo: ^repo} = lock ->
           verify_inner_checksum(repo, name, version, lock.inner_checksum)
           verify_outer_checksum(repo, name, version, lock.outer_checksum)
           verify_deps(repo, name, version, lock.deps)
@@ -599,14 +597,16 @@ defmodule Hex.RemoteConverger do
     end
   end
 
+  defp verify_deps(repo, name, version, deps)
   defp verify_deps(nil, _name, _version, _deps), do: :ok
+  defp verify_deps(_repo, _name, _version, nil), do: []
 
   defp verify_deps(repo, name, version, deps) do
     # TODO: Use requests?
     deps =
       Enum.map(deps, fn {app, req, opts} ->
         %{
-          repo: opts[:repo],
+          repo: if(opts[:repo] != "hexpm", do: opts[:repo]),
           name: opts[:hex],
           constraint: Hex.Solver.parse_constraint!(req),
           optional: !!opts[:optional],
  • test/hex/remote_converger_test.exs+50 −0 modified
    @@ -198,4 +198,54 @@ defmodule Hex.RemoteConvergerTest do
       refute_received {:mix_shell, :yes?, _}
     end)
   end
+
+  defmodule ChecksumIntegrity.MixProject do
+    def project do
+      [
+        app: :checksum_integrity,
+        version: "0.1.0",
+        deps: [
+          {:ex_doc, "~> 0.1.0"}
+        ]
+      ]
+    end
+  end
+
+  test "raises on checksum mismatch in mix.lock" do
+    in_tmp(fn ->
+      Mix.Project.push(ChecksumIntegrity.MixProject)
+
+      # First, get dependencies normally to create a valid lock file
+      :ok = Mix.Tasks.Deps.Get.run([])
+
+      # Read the lock file
+      lock = Mix.Dep.Lock.read()
+      {:hex, name, version, inner_checksum, managers, deps, repo, outer_checksum} = lock[:ex_doc]
+
+      assert_checksum_mismatch(%{
+        ex_doc:
+          {:hex, name, version, invalid_checksum(inner_checksum), managers, deps, repo,
+           outer_checksum}
+      })
+
+      assert_checksum_mismatch(%{
+        ex_doc:
+          {:hex, name, version, inner_checksum, managers, deps, repo,
+           invalid_checksum(outer_checksum)}
+      })
+    end)
+  end
+
+  defp assert_checksum_mismatch(lock) do
+    File.write!("mix.lock", inspect(lock, limit: :infinity, pretty: true))
+    Mix.Task.clear()
+
+    # The bug causes this to silently pass and rewrite the lock file with correct checksums
+    assert_raise Mix.Error, ~r/Registry checksum mismatch against lock/, fn ->
+      Mix.Tasks.Deps.Get.run([])
+    end
+  end
+
+  defp invalid_checksum("0" <> rest), do: "1" <> rest
+  defp invalid_checksum(<<_::binary-size(1), rest::binary>>), do: "0" <> rest
 end

Vulnerability mechanics

Generated by null/stub on May 9, 2026. Inputs: CWE entries + fix-commit diffs from this CVE's patches. Citations validated against bundle.

References

4

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