# CVE-2026-55156: Token Optimizer MCP: Unauthenticated Path Traversal in Dashboard Session Log API Endpoints

> Unauthenticated attackers can read arbitrary JSONL files via path traversal in the dashboard API, exposing sensitive session data.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 28 Sep 2026
- **Updated:** 28 Sep 2026
- **Also known as:** GHSA-76pc-mqxp-3rq5

## What is CVE-2026-55156?

CVE-2026-55156 is a medium-severity path traversal vulnerability in ooples token-optimizer-mcp, published on 28 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Token Optimizer MCP measures token savings per AI coding agent, optimizes context, and shares a live local knowledge graph across 16 CLI clients. Prior to version 5.1.0, the dashboard HTTP server in token-optimizer-mcp exposes /api/session-summary and /api/session-events with no authentication middleware — any network-accessible client can reach them without credentials. Both handlers concatenate the caller-supplied sessionId query parameter directly into a filesystem path via path.join, and Node.js normalizes .. segments at resolution time, allowing an unauthenticated attacker to read any .jsonl file reachable from the server's filesystem. This issue has been patched in version 5.1.0.

Weakness: CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2026-55156?

2 open source packages ship an affected version, including @ooples/token-optimizer-mcp.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `@ooples/token-optimizer-mcp` | npm | All versions | 5.1.0 |
| `@ooples/token-optimizer-mcp` | npm | All versions | 5.1.0 |

## How do I fix CVE-2026-55156?

Upgrade @ooples/token-optimizer-mcp to 5.1.0 or later.

## Is CVE-2026-55156 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55156 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-55156 and fix it if it is affected.

What it is: CVE-2026-55156 is a medium-severity path traversal vulnerability in ooples token-optimizer-mcp, published on 28 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55156 exists.

Affected packages and fixed versions:
- @ooples/token-optimizer-mcp (npm): affected all versions; fixed in 5.1.0
- @ooples/token-optimizer-mcp (npm): affected all versions; fixed in 5.1.0

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-2026-55156/ (Markdown: https://insights.sbomify.com/CVE-2026-55156/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-55156
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-55156
- OSV: https://osv.dev/vulnerability/CVE-2026-55156

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-55156/
Summaries are generated and may contain mistakes; the official description above is the record.