# CVE-2026-123535: Tornado before 6.6 Cookie Attribute Injection via set_cookie max_age


- **Severity:** Low 2.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 8 Nov 2026
- **Updated:** 12 Nov 2026
- **Also known as:** AZL-113107, CLEANSTART-2026-ZY98309, DEBIAN-CVE-2026-123535, GHSA-c6v4-qj2h-f748, GHSA-cfc4-jgx9-vvjh, UBUNTU-CVE-2026-123535

## What is CVE-2026-123535?

CVE-2026-123535 is a low-severity vulnerability in tornadoweb tornado, published on 8 Nov 2026. 

### Official description

Tornado before 6.6 does not validate the max_age argument of RequestHandler.set_cookie (also called by set_signed_cookie, set_secure_cookie, and clear_cookie), allowing injection of additional Set-Cookie attributes. When an application passes attacker-influenced input as max_age, an attacker can embed attributes such as Domain, Path, or Secure to widen the cookie's scope to parent paths or other subdomains.

Weakness: CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component)

## Which versions are affected by CVE-2026-123535?


## How do I fix CVE-2026-123535?

Upgrade to a fixed version.

## Is CVE-2026-123535 being exploited?

There is no known exploitation of CVE-2026-123535 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-123535 and fix it if it is affected.

What it is: CVE-2026-123535 is a low-severity vulnerability in tornadoweb tornado, published on 8 Nov 2026. 
Exploitation: There is no known exploitation of CVE-2026-123535 in the wild and no public exploit code.

Affected product: tornadoweb tornado. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-123535/ (Markdown: https://insights.sbomify.com/CVE-2026-123535/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-123535
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-123535
- OSV: https://osv.dev/vulnerability/CVE-2026-123535

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-123535/
Summaries are generated and may contain mistakes; the official description above is the record.