critical · 10 Patched

EPyT-Flow vulnerable to unsafe JSON deserialization (__type__)

CVE-2026-25632 · GHSA-74vm-8frp-7w68 · PYSEC-2026-330 · published 4 Feb 2026

How serious is it

  • Severity: critical, CVSS score 10 out of 10.
  • No exploit prediction (EPSS) score yet.
  • Not on the CISA list of exploited vulnerabilities.
  • No public exploit in Exploit-DB.

Is your app affected by CVE-2026-25632?

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Who is affected

  • epyt-flow (PyPI) < 0.16.1

How to check

  1. Run pip show epyt-flow in your project to see the installed version, including copies pulled in by other packages.
  2. Or paste your lockfile into the checker: it lists every package with a known vulnerability, this one included.
  3. Or run npx shippable-dev scan localhost:3000 in your project folder. It reads your lockfile and flags this vulnerability along with every other known one.

How to fix

Copies a prompt for Claude Code, Cursor or Codex: it checks your lockfiles for this and upgrades it.
  1. Upgrade epyt-flow to 0.16.1 or later, commit the lockfile and redeploy.
  2. If a vulnerable version was live, check your logs and rotate the secrets that server could read.

The advisory

### Impact EPyT-Flow’s REST API parses attacker-controlled JSON request bodies using a custom deserializer (my_load_from_json) that supports a __type__ field. When __type__ is present, the deserializer dynamically imports an attacker-specified module/class and instantiates it with attacker-supplied arguments. This allows invoking dangerous classes such as subprocess.Popen, which can lead to OS command execution during JSON parsing. This also affects the loading of JSON files. ### Patches EPyT-Flow has been patched in 0.16.1 -- affects all versions <= 0.16.0 ### Workarounds Do not load any JSON from untrusted sources and do not expose the REST API. ### Credits EPyT-Flow thanks Jarrett Chan (@syphonetic) for detecting and reporting the bug.

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References

Merged from GitHub Advisory Database, OSV. Last updated 28 Oct 2026. All vulnerabilities · RSS · JSON

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