# CVE-2026-64857: tirreno has Session Fixation in Login Authentication


- **Severity:** Medium 5.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 9 Sep 2026
- **Updated:** 9 Sep 2026
- **Also known as:** GHSA-gwcm-4p9m-9mvr

## What is CVE-2026-64857?

CVE-2026-64857 is a medium-severity vulnerability in tirrenotechnologies tirreno, published on 9 Sep 2026. 

### Official description

tirreno, a security framework, has a session fixation issue in versions prior to 0.10.0. During authentication, tirreno validates the user's credentials and establishes the authenticated session, but it does not call `session_regenerate_id()` afterward. As a result, the session identifier is not rotated on login, it stays the same before and after authentication. An attacker able to fix a known session identifier in a victim's browser (for example through a network man-in-the-middle position, or a separate cross-site scripting or subdomain cookie-injection issue) could then gain access to the victim's authenticated session. The issue is fixed in v0.10.0. The session identifier is now regenerated on successful authentication, and the previous session is destroyed. There is no configuration-level workaround.

Weakness: CWE-384 (Session Fixation)

## Which versions are affected by CVE-2026-64857?


## How do I fix CVE-2026-64857?

No fix has been published for CVE-2026-64857 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-64857 being exploited?

There is no known exploitation of CVE-2026-64857 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-64857 and fix it if it is affected.

What it is: CVE-2026-64857 is a medium-severity vulnerability in tirrenotechnologies tirreno, published on 9 Sep 2026. 
Exploitation: There is no known exploitation of CVE-2026-64857 in the wild and no public exploit code.

Affected product: tirrenotechnologies tirreno. 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-2026-64857/ (Markdown: https://insights.sbomify.com/CVE-2026-64857/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64857
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64857
- OSV: https://osv.dev/vulnerability/CVE-2026-64857

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-64857/
Summaries are generated and may contain mistakes; the official description above is the record.