Uncontrolled Recursion vulnerability in the Elixir standard library allows an attacker who controls a list passed to inspect/1, List.to_string/1, or List.to_charlist/1 to exhaust a BEAM node's memory.
Inspect.List's charlist branch in lib/elixir/lib/inspect.ex classifies a list as a charlist using List.ascii_printable?/2, which examines only the first :printable_limit (4096 by default) elements, and then calls IO.chardata_to_string/1 on the whole term. A list whose printable prefix exceeds that limit but which contains a later element that is not a code point (an atom, an out-of-range integer, or an improper tail) is therefore mis-classified, and the conversion raises ArgumentError. That conversion runs inside List.to_string/1, whose rescue clause builds its message by interpolating inspect(list), which re-enters the same branch and raises again. The nested inspection is an argument to raise, so the recursion is not in tail position and every level is retained: the process stack grows monotonically while each cycle re-walks the list, until the process is killed by max_heap_size or, by default, the node runs out of memory. List.to_charlist/1 has the same rescue shape.
Below the printable limit the inner inspect/1 sees the invalid element within its counter and renders the list in ordinary bracket form, so a single ArgumentError is raised and no recursion occurs.
This issue affects elixir: from 1.15.0-rc.0 before 1.18.5, from 1.19.0-rc.0 before 1.19.6, and from 1.20.0-rc.0 before 1.20.4.
" }, { "base64": false, "type": "text/markdown", "value": "Uncontrolled Recursion vulnerability in the Elixir standard library allows an attacker who controls a list passed to `inspect/1`, `List.to_string/1`, or `List.to_charlist/1` to exhaust a BEAM node's memory.\n\n`Inspect.List`'s charlist branch in `lib/elixir/lib/inspect.ex` classifies a list as a charlist using `List.ascii_printable?/2`, which examines only the first `:printable_limit` (4096 by default) elements, and then calls `IO.chardata_to_string/1` on the whole term. A list whose printable prefix exceeds that limit but which contains a later element that is not a code point (an atom, an out-of-range integer, or an improper tail) is therefore mis-classified, and the conversion raises `ArgumentError`. That conversion runs inside `List.to_string/1`, whose rescue clause builds its message by interpolating `inspect(list)`, which re-enters the same branch and raises again. The nested inspection is an argument to `raise`, so the recursion is not in tail position and every level is retained: the process stack grows monotonically while each cycle re-walks the list, until the process is killed by `max_heap_size` or, by default, the node runs out of memory. `List.to_charlist/1` has the same rescue shape.\n\nBelow the printable limit the inner `inspect/1` sees the invalid element within its counter and renders the list in ordinary bracket form, so a single `ArgumentError` is raised and no recursion occurs.\n\nThis issue affects elixir: from 1.15.0-rc.0 before 1.18.5, from 1.19.0-rc.0 before 1.19.6, and from 1.20.0-rc.0 before 1.20.4." } ], "value": "Uncontrolled Recursion vulnerability in the Elixir standard library allows an attacker who controls a list passed to inspect/1, List.to_string/1, or List.to_charlist/1 to exhaust a BEAM node's memory.\n\nInspect.List's charlist branch in lib/elixir/lib/inspect.ex classifies a list as a charlist using List.ascii_printable?/2, which examines only the first :printable_limit (4096 by default) elements, and then calls IO.chardata_to_string/1 on the whole term. A list whose printable prefix exceeds that limit but which contains a later element that is not a code point (an atom, an out-of-range integer, or an improper tail) is therefore mis-classified, and the conversion raises ArgumentError. That conversion runs inside List.to_string/1, whose rescue clause builds its message by interpolating inspect(list), which re-enters the same branch and raises again. The nested inspection is an argument to raise, so the recursion is not in tail position and every level is retained: the process stack grows monotonically while each cycle re-walks the list, until the process is killed by max_heap_size or, by default, the node runs out of memory. List.to_charlist/1 has the same rescue shape.\n\nBelow the printable limit the inner inspect/1 sees the invalid element within its counter and renders the list in ordinary bracket form, so a single ArgumentError is raised and no recursion occurs.\n\nThis issue affects elixir: from 1.15.0-rc.0 before 1.18.5, from 1.19.0-rc.0 before 1.19.6, and from 1.20.0-rc.0 before 1.20.4." } ], "impacts": [ { "capecId": "CAPEC-130", "descriptions": [ { "lang": "en", "value": "CAPEC-130 Excessive Allocation" } ] } ], "metrics": [ { "cvssV4_0": { "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "attackVector": "LOCAL", "baseScore": 5.9, "baseSeverity": "MEDIUM", "privilegesRequired": "NONE", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "userInteraction": "NONE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N", "version": "4.0", "vulnAvailabilityImpact": "HIGH", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnerabilityResponseEffort": "NOT_DEFINED" }, "format": "CVSS", "scenarios": [ { "lang": "en", "value": "GENERAL" } ] } ], "problemTypes": [ { "descriptions": [ { "cweId": "CWE-674", "description": "CWE-674 Uncontrolled Recursion", "lang": "en", "type": "CWE" } ] } ], "providerMetadata": { "orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "shortName": "EEF", "dateUpdated": "2026-08-28T11:28:53.505Z" }, "references": [ { "tags": [ "vendor-advisory", "related" ], "url": "https://github.com/elixir-lang/elixir/security/advisories/GHSA-jf5q-v438-665c" }, { "tags": [ "related" ], "url": "https://cna.erlef.org/cves/CVE-2026-75758.html" }, { "tags": [ "related" ], "url": "https://osv.dev/vulnerability/EEF-CVE-2026-75758" }, { "tags": [ "patch" ], "url": "https://github.com/elixir-lang/elixir/commit/1eff1acffd49bdcc0d7f57ca74c1603328eed68a" }, { "tags": [ "patch" ], "url": "https://github.com/elixir-lang/elixir/commit/5230d73968f1b4969d2a2646786fa6c71475f5cc" }, { "tags": [ "patch" ], "url": "https://github.com/elixir-lang/elixir/commit/a983c8c043b1fbf1d95df78a29149222dac2988c" }, { "tags": [ "patch" ], "url": "https://github.com/elixir-lang/elixir/commit/0bba5887577b1e328da825bd018815fdc519685a" } ], "source": { "discovery": "EXTERNAL" }, "title": "Unbounded recursion between Inspect.List charlist rendering and List.to_string/1 error path in Elixir", "workarounds": [ { "lang": "en", "supportingMedia": [ { "base64": false, "type": "text/html", "value": "Install a global inspect function that renders lists as lists rather than inferring charlists, by calling Inspect.Opts.default_inspect_fun/1 with fn term, opts -> Inspect.inspect(term, %{opts | charlists: :as_lists}) end from the application's start callback. This keeps the charlist branch from being entered at all, so the mis-inferred conversion never raises and the error path cannot recurse.
The trade-off is global: charlists then render in bracket form, so ~c\"abc\" inspects as [97, 98, 99] everywhere in the application, including in logs and error reports.