PDF Reader MCP: HTTP transport accepts unauthenticated requests despite a configured MCP_API_KEY

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

PDF Reader MCP is a Model Context Protocol server for reading PDF documents. In versions 2.2.0 and later prior to 3.0.1, when `MCP_TRANSPORT=http` enables the opt-in HTTP server, `@sylphx/pdf-reader-mcp` reads `MCP_API_KEY` and logs that `X-API-Key` authentication is enabled but never validates the `X-API-Key` header on incoming requests. The `/mcp` endpoint consequently accepts unauthenticated clients. With the default bind address of `0.0.0.0`, any client able to reach the port can invoke every PDF tool and read any PDF the server process can open on the host, despite the misleading authentication-enabled startup log. URL-based sources additionally permit limited server-side request forgery; private and loopback destinations are blocked by default unless `--allow-private-ips` is set. The default `stdio` transport is unaffected. This issue is fixed in version 3.0.1.

Source published

30 Oct 2026 18:32:18 UTC

Source modified

6 Nov 2026 17:26:07 UTC

Observed here

6 Nov 2026 19:02:40 UTC

Source terms

CVE Program Terms of Use

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CVSS 3.1 · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

PDF Reader MCP is a Model Context Protocol server for reading PDF documents. In versions 2.2.0 and later prior to 3.0.1, when `MCP_TRANSPORT=http` enables the opt-in HTTP server, `@sylphx/pdf-reader-mcp` reads `MCP_API_KEY` and logs that `X-API-Key` authentication is enabled but never validates the `X-API-Key` header on incoming requests. The `/mcp` endpoint consequently accepts unauthenticated clients. With the default bind address of `0.0.0.0`, any client able to reach the port can invoke every PDF tool and read any PDF the server process can open on the host, despite the misleading authentication-enabled startup log. URL-based sources additionally permit limited server-side request forgery; private and loopback destinations are blocked by default unless `--allow-private-ips` is set. The default `stdio` transport is unaffected. This issue is fixed in version 3.0.1.

Source published

Oct 30, 2026, 6:32:18 PM (timezone not stated)

Source modified

Nov 6, 2026, 5:26:07 PM (timezone not stated)

Observed here

6 Nov 2026 19:05:55 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 3.1 · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

PDF Reader MCP is a Model Context Protocol server for reading PDF documents. In versions 2.2.0 and later prior to 3.0.1, when `MCP_TRANSPORT=http` enables the opt-in HTTP server, `@sylphx/pdf-reader-mcp` reads `MCP_API_KEY` and logs that `X-API-Key` authentication is enabled but never validates the `X-API-Key` header on incoming requests. The `/mcp` endpoint consequently accepts unauthenticated clients. With the default bind address of `0.0.0.0`, any client able to reach the port can invoke every PDF tool and read any PDF the server process can open on the host, despite the misleading authentication-enabled startup log. URL-based sources additionally permit limited server-side request forgery; private and loopback destinations are blocked by default unless `--allow-private-ips` is set. The default `stdio` transport is unaffected. This issue is fixed in version 3.0.1.

Source published

30 Oct 2026 19:18:32 UTC

Source modified

6 Nov 2026 18:18:16 UTC

Observed here

6 Nov 2026 19:10:24 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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CVSS 3.1 · [email protected] · Secondary · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

### Impact When `@sylphx/pdf-reader-mcp` is run as an HTTP server (`MCP_TRANSPORT=http`), it reads the `MCP_API_KEY` environment variable and logs `API key authentication enabled (X-API-Key header)` at startup, but it never validated the `X-API-Key` header on incoming requests. The key was read into a variable and never enforced on the request path. As a result, the `/mcp` endpoint accepted **unauthenticated** requests. Combined with the default bind address of `0.0.0.0` (all interfaces), any client able to reach the port could invoke every PDF tool and read the contents of any PDF the server process could open anywhere on the host. URL-based sources also enable limited SSRF (private/loopback addresses are blocked by default unless `--allow-private-ips` is set). The misleading startup log made the exposure silent: an operator who set `MCP_API_KEY` reasonably believed the server was protected when it was not. This affects only the opt-in HTTP transport; the default `stdio` transport is unaffected. ### Patches Fixed in `@sylphx/[email protected]`. The fix enforces the `X-API-Key` header with a constant-time comparison (rejecting missing/mismatched keys with HTTP 401), changes the default bind host to `127.0.0.1` (loopback), and emits a startup warning when binding a non-loopback host without an API key. ### Workarounds For deployments that cannot upgrade immediately: - Bind to loopback only: `MCP_HTTP_HOST=127.0.0.1`. - Place a reverse proxy in front that enforces authentication. - Use the default `stdio` transport instead of HTTP. - Restrict filesystem reach with `--allow-dir` / `MCP_PDF_ALLOWED_DIRS`. Reported privately by **novice-22** via responsible disclosure.

Source published

29 Oct 2026 16:34:35 UTC

Source modified

29 Oct 2026 16:45:05 UTC

Observed here

29 Oct 2026 17:12:42 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Publisher rating · HIGH