VulnerabilityPublished 14 May 2026Updated 16 May 2026

CVE-2026-45781: modelcontextprotocol registry · Failing Open

Affects modelcontextprotocol registrySource CVE Database V5

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Not known to be exploited · CVSS 3.5 Low : upgrade to 1.7.9 when convenient.

Data as of 29 Oct 2026, 19:04 UTC

CVSS 3.1 base score

3.5Low

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.2% chance of exploitation in 30 days – higher than 14% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 1.7.9

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: Low
User Interaction: Required
Scope: Unchanged
Confidentiality: None
Integrity: Low
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 14 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade modelcontextprotocol registry to 1.7.9.

Affected software

Product	Affected	Fixed in
modelcontextprotocolregistry	Affected <1.7.9	Fixed in 1.7.9

AI-suggested

Upgrade the MCP Registry to version 1.7.9 or later, where this vulnerability is fixed. Prior to upgrading, be aware that the registry fails open on HTTP 429 responses from the upstream OCI registry, allowing ownership validation bypass. No other mitigations are documented. Patch status is not explicitly stated but the fix is included in version 1.7.9.

Description

CVE-2026-45781 is a vulnerability in the modelcontextprotocol (MCP) registry prior to version 1.7.9. The issue arises because the OCI ownership validation fails open when the upstream OCI registry returns an HTTP 429 (Too Many Requests) response. This failure allows any authenticated publisher to bind namespaces they do not control to OCI images, bypassing the critical label-match ownership check. The vulnerability is specific to OCI packages; other package types enforce stricter validation. This flaw has a low severity score and no known exploits in the wild. A fix was introduced in version 1.7.9.

Impact

The vulnerability allows authenticated publishers to bypass ownership validation for OCI images under certain rate-limiting conditions, potentially enabling unauthorized namespace binding. This could lead to integrity issues in the MCP Registry's handling of OCI packages. The impact is limited to integrity (no confidentiality or availability impact) and is rated low severity with a CVSS score of 3.5. There are no known exploits in the wild.

Summary

The MCP Registry provides clients with a list of MCP servers and validates ownership of OCI images by checking a label-match in the upstream OCI registry. Before version 1.7.9, when the upstream OCI registry rate-limits requests (HTTP 429), the validation function ValidateOCI incorrectly returns success without performing the label-match check. This 'fail open' behavior (CWE-636) allows authenticated publishers to bind namespaces they do not own, compromising ownership integrity for OCI packages. Other package types treat non-200 responses as errors, preventing this bypass. The vulnerability is fixed in MCP Registry version 1.7.9.

CWE-636Not Failing Securely (Failing Open) (opens in a new tab)
Class weaknessOWASP Top 10 A10:2025: Mishandling of Exceptional Conditions (opens in a new tab)
When the product encounters an error condition or failure, its design requires it to fall back to a state that is less secure than other options that are available, such as selecting the weakest encryption algorithm or using the most permissive access control restrictions.
Architecture and Design
Subdivide and allocate resources and components so that a failure in one part does not affect the entire product.
OWASP Cheat Sheets
Logging (opens in a new tab)
Error Handling (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

github.com/modelcontextprotocol/registry/security/advisories/GHSA-2v5f-5r6w-p67r (opens in a new tab)

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 22 May 2026, 15:31 UTC

WeaknessesCWE-636

Technical details

References

Community reviews

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