Description
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.
Published: 2026-08-28
Score: 5.9 Medium
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
AI Analysis

Impact

Unbounded recursion occurs when Elixir’s inspect/1 misclassifies a list as a charlist due to only examining the first 4096 elements for printability. When a long printable prefix is followed by an element that is not a valid code point, the conversion raises an ArgumentError. The rescue clause in List.to_string/1 rebuilds its error message by inspecting the list again, which re-enters the same misclassification path. Because the recursion is not in tail position, each level of inspection adds a frame to the process stack, steadily consuming memory until the BEAM node’s max_heap_size is exceeded or the node runs out of memory. This results in a crash for the process and can bring down the entire node if no safeguards are in place.

Affected Systems

This vulnerability affects the Elixir language standard library. All released Elixir versions from 1.15.0‑rc.0 up to but not including 1.18.5, from 1.19.0‑rc.0 up to but not including 1.19.6, and from 1.20.0‑rc.0 up to but not including 1.20.4 are vulnerable. The affected product is the Elixir compiler and runtime, maintained by elixir‑lang.

Risk and Exploitability

The CVSS score of 5.9 indicates moderate severity. The EPSS score is not available, so the current exploitation probability is uncertain, and the vulnerability is not listed in the CISA KEV catalog. An attacker must be able to supply a crafted list to inspect/1, List.to_string/1, or List.to_charlist/1 – for example, by sending a malicious payload to an exposed API that internally calls these functions. The attack is relatively straightforward and does not require privileged code execution; it exploits a flaw in the language’s standard library that causes uncontrolled recursion and memory exhaustion.

Generated by OpenCVE AI on August 28, 2026 at 16:53 UTC.

Remediation

Vendor Workaround

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.

OpenCVE Recommended Actions

  • Install a global inspect function that forces list rendering as lists by configuring Inspect.Opts.default_inspect_fun/1 with the option charlists: :as_lists during application startup; this prevents the charlist branch from being entered and stops the recursion.
  • Upgrade Elixir to a recent released version: 1.18.5 or later, 1.19.6 or later, or 1.20.4 or later, which contain the patch for this recursion issue.
  • Configure appropriate BEAM memory limits (e.g., set --max-heap-size and use TELEMETRY or metrics to detect and restart overloaded nodes) and validate user input to avoid passing untrusted lists to inspect/1 or the string conversion functions.

Generated by OpenCVE AI on August 28, 2026 at 16:53 UTC.

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History

Fri, 28 Aug 2026 15:30:00 +0000

Type Values Removed Values Added
Description 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.
Title Unbounded recursion between Inspect.List charlist rendering and List.to_string/1 error path in Elixir
First Time appeared Elixir-lang
Elixir-lang elixir
Weaknesses CWE-674
CPEs cpe:2.3:a:elixir-lang:elixir:*:*:*:*:*:*:*:*
Vendors & Products Elixir-lang
Elixir-lang elixir
References
Metrics cvssV4_0

{'score': 5.9, 'vector': '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'}

Subscriptions

Elixir-lang Elixir
cve-icon MITRE

Status: PUBLISHED

Assigner: EEF

Published:

Updated: 2026-08-28T11:28:53.505Z

Reserved: 2026-08-19T09:00:01.955Z

Link: CVE-2026-75758

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-08-28T16:18:25.277

Modified: 2026-08-28T16:18:25.277

Link: CVE-2026-75758

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-08-28T17:00:13Z

Weaknesses