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NVD / CVE Program· CNA GitHub_M

CVE-2026-111771: Model Context Protocol TypeScript SDK: Server bearer authentication accepted tokens issued for another service

MediumCVSS 6.8 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 27/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.54% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. A low-privileged account is enough. No user action is required. Special conditions such as timing or configuration are required.
  • Fixed version: @modelcontextprotocol/express (npm) 2.0.2; @modelcontextprotocol/sdk (npm) 1.32.0; @modelcontextprotocol/server (npm) 2.3.0.

Low priority for now. Upgrade to @modelcontextprotocol/express (npm) 2.0.2; @modelcontextprotocol/sdk (npm) 1.32.0; @modelcontextprotocol/server (npm) 2.3.0 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

The Model Context Protocol TypeScript SDK provides TypeScript client and server implementations of the Model Context Protocol. From 1.6.0 until 1.32.0 in @modelcontextprotocol/sdk, from 2.0.0 until 2.3.0 in @modelcontextprotocol/server, from 2.0.0 until 2.0.2 in @modelcontextprotocol/express, and from 2.0.0 until 2.3.1 in @modelcontextprotocol/server-legacy, server-side bearer authentication could accept a valid access token issued for a different service because the SDK did not enforce the token audience. The affected surface is server-side HTTP bearer authentication. The trigger is a valid token whose audience names another service. The authorization server must issue tokens for multiple services, and the application's verifyAccessToken() must not independently validate aud. Applications already validating aud inside verifyAccessToken() are not affected. An attacker with a token for another service could authenticate to the MCP server and obtain the confidentiality and integrity capabilities granted to an authenticated caller. Upgrading alone leaves the new audience validation disabled. Operators must enable audience validation and provide the token audience together. Enabling only the expected audience check causes every request to receive HTTP 401. This issue is fixed in @modelcontextprotocol/sdk 1.32.0, @modelcontextprotocol/server 2.3.0, @modelcontextprotocol/express 2.0.2, and @modelcontextprotocol/server-legacy 2.3.1.

Published
Nov 5, 2026
Updated
Nov 12, 2026
EPSS
0.5% · 46th percentile

Report tools

JSON

Action score

27

Monitor

Low priority for now.

CVSS
27 / 40 · 6.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.5%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · GitHub_M
6.8
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

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When you'll hear from us

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  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

  • @modelcontextprotocol express

    • >= 2.0.0, < 2.0.2affected

  • @modelcontextprotocol sdk

    • >= 1.6.0, < 1.32.0affected

  • @modelcontextprotocol server

    • >= 2.0.0, < 2.3.0affected

  • @modelcontextprotocol server-legacy

    • >= 2.0.0, < 2.3.1affected

  • modelcontextprotocol typescript-sdk

    • >= 1.6.0, < 1.32.0affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
npm@modelcontextprotocol/expressfrom 2.0.0 · before 2.0.22.0.2
npm@modelcontextprotocol/sdkfrom 1.6.0 · before 1.32.01.32.0
npm@modelcontextprotocol/serverfrom 2.0.0 · before 2.3.02.3.0
npm@modelcontextprotocol/server-legacyfrom 2.0.0 · before 2.3.12.3.1

Same product

modelcontextprotocol: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-111767MCP TypeScript SDK: Experimental tasks were not tied to the session that created them
    34Monitor
  • CVE-2026-111770Model Context Protocol TypeScript SDK: Shared transport or server instances delivered one HTTP client's messages to another
    30Monitor
  • CVE-2026-111768Model Context Protocol TypeScript SDK: One HTTP request within the default size limit could exhaust server memory during validation
    30Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2026-104850Oct 6, 2026 · MCP TypeScript SDK: OAuth client could send credentials to an authorization server chosen by the MCP server
    30Monitor
  • Later →CVE-2026-111769Nov 5, 2026 · Model Context Protocol TypeScript SDK: HTTP client transports and OAuth requests followed cross-origin redirects and re-sent custom headers and request bodies
    26Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
npm:@modelcontextprotocol/express2.0.2Package registry (OSV)
npm:@modelcontextprotocol/sdk1.32.0Package registry (OSV)
npm:@modelcontextprotocol/server2.3.0Package registry (OSV)
npm:@modelcontextprotocol/server-legacy2.3.1Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Published
  2. Fix recordedsame day
  3. TodayNov 13, 2026+8 d
EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Not on record for this CVE: researcher credit · variant or chain candidate · public bounty program.

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
none
Attack vector
Network
Attack complexity
High
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
None

Weakness class (CWE)

CWE-863 · Incorrect Authorization

CVSS vector

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

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. SSVC exploitation— → none
  2. Fix✗ → ✓
  3. Exploit maturity— → none

For records you follow, these changes also arrive as notifications. →

References

Show all references (10 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records