{ "document": { "category": "csaf_base", "csaf_version": "2.0", "distribution": { "tlp": { "label": "WHITE" } }, "lang": "en", "notes": [ { "category": "legal_disclaimer", "text": "The Netherlands Cyber Security Center (henceforth: NCSC-NL) maintains this portal to enhance access to its information and vulnerabilities. The use of this information is subject to the following terms and conditions:\n\nThe vulnerabilities disclosed in this portal are gathered by NCSC-NL from a variety of open sources, which the user can retrieve from other platforms. NCSC-NL makes every reasonable effort to ensure that the content of this portal is kept up to date, and that it is accurate and complete. Nevertheless, NCSC-NL cannot entirely rule out the possibility of errors, and therefore cannot give any warranty in respect of its completeness, accuracy or real-time keeping up-to-date. NCSC-NL does not control nor guarantee the accuracy, relevance, timeliness or completeness of information obtained from these external sources. The vulnerabilities disclosed in this portal are intended solely for the convenience of professional parties to take appropriate measures to manage the risks posed to the cybersecurity. No rights can be derived from the information provided therein.\n\nNCSC-NL and the Kingdom of the Netherlands assume no legal liability or responsibility for any damage resulting from either the use or inability of use of the vulnerabilities disclosed in this portal. This includes damage resulting from the inaccuracy of incompleteness of the information contained in it.\nThe information on this page is subject to Dutch law. All disputes related to or arising from the use of this portal regarding the disclosure of vulnerabilities will be submitted to the competent court in The Hague. This choice of means also applies to the court in summary proceedings." } ], "publisher": { "category": "coordinator", "contact_details": "cert@ncsc.nl", "name": "National Cyber Security Centre", "namespace": "https://www.ncsc.nl/" }, "title": "CVE-2026-34593", "tracking": { "current_release_date": "2026-04-03T15:31:36.936858Z", "generator": { "date": "2026-02-17T15:00:00Z", "engine": { "name": "V.E.L.M.A", "version": "1.7" } }, "id": "CVE-2026-34593", "initial_release_date": "2026-04-01T01:03:15.536863Z", "revision_history": [ { "date": "2026-04-01T01:03:15.536863Z", "number": "1", "summary": "CVE created.| Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| References created (4).| CWES updated (1)." }, { "date": "2026-04-01T01:03:29.229682Z", "number": "2", "summary": "NCSC Score created." }, { "date": "2026-04-02T18:26:59.688815Z", "number": "3", "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| References created (2).| CWES updated (1)." }, { "date": "2026-04-02T18:27:01.843416Z", "number": "4", "summary": "NCSC Score updated." }, { "date": "2026-04-02T18:48:08.961246Z", "number": "5", "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| Products created (1).| References created (2).| CWES updated (1)." }, { "date": "2026-04-02T18:48:11.258347Z", "number": "6", "summary": "NCSC Score updated." }, { "date": "2026-04-03T13:39:27.161345Z", "number": "7", "summary": "Unknown change." }, { "date": "2026-04-03T13:39:32.645118Z", "number": "8", "summary": "NCSC Score updated." }, { "date": "2026-04-03T15:31:13.370725Z", "number": "9", "summary": "Source connected.| CVE status created. (valid)| EPSS created." }, { "date": "2026-04-03T15:31:23.389055Z", "number": "10", "summary": "NCSC Score updated." } ], "status": "interim", "version": "10" } }, "product_tree": { "branches": [ { "branches": [ { "branches": [ { "category": "product_version_range", "name": "vers:unknown/<3.22.0", "product": { "name": "vers:unknown/<3.22.0", "product_id": "CSAFPID-5985240" } } ], "category": "product_name", "name": "ash" } ], "category": "vendor", "name": "ash-project" } ] }, "vulnerabilities": [ { "cve": "CVE-2026-34593", "notes": [ { "category": "description", "text": "## Summary\n\n`Ash.Type.Module.cast_input/2` unconditionally creates a new Erlang atom via `Module.concat([value])` for any user-supplied binary string that starts with `\"Elixir.\"`, before verifying whether the referenced module exists. Because Erlang atoms are never garbage-collected and the BEAM atom table has a hard default limit of approximately 1,048,576 entries, an attacker who can submit values to any resource attribute or argument of type `:module` can exhaust this table and crash the entire BEAM VM, taking down the application.\n\n## Details\n\n**Setup**: A resource with a `:module`-typed attribute exposed to user input, which is a supported and documented usage of the `Ash.Type.Module` built-in type:\n\n```elixir\ndefmodule MyApp.Widget do\n use Ash.Resource, domain: MyApp, data_layer: AshPostgres.DataLayer\n\n attributes do\n uuid_primary_key :id\n attribute :handler_module, :module, public?: true\n end\n\n actions do\n defaults [:read, :destroy]\n create :create do\n accept [:handler_module]\n end\n end\nend\n```\n\n**Vulnerable code** in `lib/ash/type/module.ex`, lines 105-113:\n\n```elixir\ndef cast_input(\"Elixir.\" <> _ = value, _) do\n module = Module.concat([value]) # <-- Creates new atom unconditionally\n if Code.ensure_loaded?(module) do\n {:ok, module}\n else\n :error # <-- Returns error but atom is already created\n end\nend\n```\n\n**Exploit**: Submit repeated `Ash.create` requests (e.g., via a JSON API endpoint) with unique `\"Elixir.*\"` strings:\n\n```elixir\n# Attacker-controlled loop (or HTTP requests to an API endpoint)\nfor i <- 1..1_100_000 do\n Ash.Changeset.for_create(MyApp.Widget, :create, %{handler_module: \"Elixir.Attack#{i}\"})\n |> Ash.create()\n # Each iteration: Module.concat([\"Elixir.Attack#{i}\"]) creates a new atom\n # cast_input returns :error but the atom :\"Elixir.Attack#{i}\" persists\nend\n# After ~1,048,576 unique strings: BEAM crashes with system_limit\n```\n\n**Contrast**: The non-`\"Elixir.\"` path in the same function correctly uses `String.to_existing_atom/1`, which is safe because it only looks up atoms that already exist:\n\n```elixir\ndef cast_input(value, _) when is_binary(value) do\n atom = String.to_existing_atom(value) # safe - raises if atom doesn't exist\n ...\nend\n```\n\n**Additional occurrence**: `cast_stored/2` at line 141 contains the identical pattern, which is reachable when reading `:module`-typed values from the database if an attacker can write arbitrary `\"Elixir.*\"` strings to the relevant database column.\n\n## Impact\n\nAn attacker who can submit requests to any API endpoint backed by an Ash resource with a `:module`-typed attribute or argument can crash the entire BEAM VM process. This is a complete denial of service: all resources served by that VM instance (not just the targeted resource) become unavailable. The crash cannot be prevented once the atom table is full, and recovery requires a full process restart.\n\n**Fix direction**: Replace `Module.concat([value])` with `String.to_existing_atom(value)` wrapped in a `rescue ArgumentError` block (as already done in the non-`\"Elixir.\"` branch), or validate that the atom already exists before calling `Module.concat` by first attempting `String.to_existing_atom` and only falling back to `Module.concat` on success.", "title": "github - https://api.github.com/advisories/GHSA-jjf9-w5vj-r6vp" }, { "category": "description", "text": "Ash Framework is a declarative, extensible framework for building Elixir applications. Prior to version 3.22.0, Ash.Type.Module.cast_input/2 unconditionally creates a new Erlang atom via Module.concat([value]) for any user-supplied binary string that starts with \"Elixir.\", before verifying whether the referenced module exists. Because Erlang atoms are never garbage-collected and the BEAM atom table has a hard default limit of approximately 1,048,576 entries, an attacker who can submit values to any resource attribute or argument of type :module can exhaust this table and crash the entire BEAM VM, taking down the application. This issue has been patched in version 3.22.0.", "title": "nvd - https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-34593" }, { "category": "description", "text": "Ash Framework is a declarative, extensible framework for building Elixir applications. Prior to version 3.22.0, Ash.Type.Module.cast_input/2 unconditionally creates a new Erlang atom via Module.concat([value]) for any user-supplied binary string that starts with \"Elixir.\", before verifying whether the referenced module exists. Because Erlang atoms are never garbage-collected and the BEAM atom table has a hard default limit of approximately 1,048,576 entries, an attacker who can submit values to any resource attribute or argument of type :module can exhaust this table and crash the entire BEAM VM, taking down the application. This issue has been patched in version 3.22.0.", "title": "cveprojectv5 - https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/34xxx/CVE-2026-34593.json" }, { "category": "other", "text": "0.00042", "title": "EPSS" }, { "category": "other", "text": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N", "title": "CVSSV4" }, { "category": "other", "text": "8.2", "title": "CVSSV4 base score" }, { "category": "other", "text": "4.0", "title": "NCSC Score" }, { "category": "other", "text": "Is related to CWE-400 (Uncontrolled Resource Consumption)", "title": "NCSC Score top increasing factors" }, { "category": "other", "text": "The value of the most recent CVSS (V3) score, There is cwe data available from source Nvd", "title": "NCSC Score top decreasing factors" } ], "product_status": { "known_affected": [ "CSAFPID-5985240" ] }, "references": [ { "category": "external", "summary": "Source - github", "url": "https://api.github.com/advisories/GHSA-jjf9-w5vj-r6vp" }, { "category": "external", "summary": "Source - nvd", "url": "https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-34593" }, { "category": "external", "summary": "Source - cveprojectv5", "url": "https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/34xxx/CVE-2026-34593.json" }, { "category": "external", "summary": "Source - first", "url": "https://api.first.org/data/v1/epss?limit=10000&offset=0" }, { "category": "external", "summary": "Reference - cveprojectv5; github; nvd", "url": "https://github.com/ash-project/ash/security/advisories/GHSA-jjf9-w5vj-r6vp" }, { "category": "external", "summary": "Reference - github", "url": "https://github.com/ash-project/ash/commit/7031103da38cd1366cec8c96d6bcdc9b989aa3c2" }, { "category": "external", "summary": "Reference - cveprojectv5; github; nvd", "url": "https://github.com/ash-project/ash/releases/tag/v3.22.0" }, { "category": "external", "summary": "Reference - github", "url": "https://github.com/advisories/GHSA-jjf9-w5vj-r6vp" } ], "title": "CVE-2026-34593" } ] }