# CVE-2026-54618: Obsidian Web MCP: Unauthenticated vault access: /oauth/authorize auto-approves without authenticating the user

> Unauthenticated attackers can bypass OAuth checks to read, write, and delete files in Obsidian vaults via the Web MCP server.

- **Severity:** Critical 9.4 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 17 Sep 2026
- **Updated:** 24 Sep 2026
- **Also known as:** GHSA-hwhg-mrjc-8g43

## What is CVE-2026-54618?

CVE-2026-54618 is a critical authentication bypass vulnerability in jimprosser obsidian-web-mcp, published on 17 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Obsidian Web MCP is a secure remote MCP server for Obsidian vaults. Prior to 0.2.0, /oauth/authorize issues an authorization code without a login, consent, or session check, and /oauth/token can exchange that code for the static VAULT_MCP_TOKEN without authenticating a client. An unauthenticated remote caller who can reach the intended tunnel deployment can therefore call /mcp and use vault_read, vault_write, vault_search, vault_list, vault_move, and vault_delete against the entire vault. Optional PKCE does not prevent an attacker-initiated flow, and unauthenticated /oauth/register also exposes a client_credentials path by returning the configured VAULT_OAUTH_CLIENT_SECRET. This issue is fixed in version 0.2.0.

Weakness: CWE-601 (URL Redirection to Untrusted Site), CWE-522 (Insufficiently Protected Credentials), CWE-306 (Missing Authentication for Critical Functionality)

## Which versions are affected by CVE-2026-54618?


## How do I fix CVE-2026-54618?

No fix has been published for CVE-2026-54618 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-54618 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-54618 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-54618 and fix it if it is affected.

What it is: CVE-2026-54618 is a critical authentication bypass vulnerability in jimprosser obsidian-web-mcp, published on 17 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-2026-54618 exists.

Affected product: jimprosser obsidian-web-mcp. 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-2026-54618/ (Markdown: https://insights.sbomify.com/CVE-2026-54618/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-54618
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-54618
- OSV: https://osv.dev/vulnerability/CVE-2026-54618

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-54618/
Summaries are generated and may contain mistakes; the official description above is the record.