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CVE-2026-45781

MCP Registry: OCI ownership validation fails open on upstream rate limits, allowing attacker-controlled package claims

3.5 LowFix available

The MCP Registry provides MCP clients with a list of MCP servers, like an app store for MCP servers. Prior to 1.7.9, OCI ownership validation skips label-match check when upstream OCI registry returns HTTP 429, letting any authenticated publisher bind their io.github.<user>/* namespace to OCI images they do not control. internal/validators/registries/oci.go:104-119 fails open on http.StatusTooManyRequests: when the registry's anonymous fetch to the upstream OCI registry is rate-limited, ValidateOCI returns nil and the publish is accepted without ever running the io.modelcontextprotocol.server.name label-match check at lines 122-141. That label check is the only cross-system ownership proof the registry applies to OCI packages — every other registry type (NPM, PyPI, NuGet, MCPB) treats a non-200 upstream response as a hard error. This vulnerability is fixed in 1.7.9.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
Low
User interaction
Required

What an attacker can affect

Confidentiality
None
Integrity
Low
Availability
None

Exploit likelihood

0.23%Up 0.2 points since May 15, 2026
90%50%10%1%

What each source reports

CVE List Score used 3.5

MCP Registry: OCI ownership validation fails open on upstream rate limits, allowing attacker-controlled package claims

The MCP Registry provides MCP clients with a list of MCP servers, like an app store for MCP servers. Prior to 1.7.9, OCI ownership validation skips label-match check when upstream OCI registry returns HTTP 429, letting any authenticated publisher bind their io.github.<user>/* namespace to OCI images they do not control. internal/validators/registries/oci.go:104-119 fails open on http.StatusTooManyRequests: when the registry's anonymous fetch to the upstream OCI registry is rate-limited, ValidateOCI returns nil and the publish is accepted without ever running the io.modelcontextprotocol.server.name label-match check at lines 122-141. That label check is the only cross-system ownership proof the registry applies to OCI packages — every other registry type (NPM, PyPI, NuGet, MCPB) treats a non-200 upstream response as a hard error. This vulnerability is fixed in 1.7.9.

Record
CVE-2026-45781
CVSS 3.1
3.5 LowCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N
Weakness
CWE-636
Updated
2026-11-02
EUVDEUVD-2026-30489 3.5

The MCP Registry provides MCP clients with a list of MCP servers, like an app store for MCP servers. Prior to 1.7.9, OCI ownership validation skips label-match check when upstream OCI registry returns HTTP 429, letting any authenticated publisher bind their io.github.<user>/* namespace to OCI images they do not control. internal/validators/registries/oci.go:104-119 fails open on http.StatusTooManyRequests: when the registry's anonymous fetch to the upstream OCI registry is rate-limited, ValidateOCI returns nil and the publish is accepted without ever running the io.modelcontextprotocol.server.name label-match check at lines 122-141. That label check is the only cross-system ownership proof the registry applies to OCI packages — every other registry type (NPM, PyPI, NuGet, MCPB) treats a non-200 upstream response as a hard error. This vulnerability is fixed in 1.7.9.

Record
EUVD-2026-30489
CVSS 3.1
3.5 LowCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-2v5f-5r6w-p67r 3.5

MCP Registry: OCI validator skips ownership check on upstream rate limits

OCI ownership validation fails open on upstream rate limits, allowing attacker to claim arbitrary public OCI images under their own namespace

Severity: Low (re-scored post-triage; see Maintainer triage note below) Affected: modelcontextprotocol/registry main branch at commit fe0cb3b (current HEAD as of 2026-05-09). Live deployment: https://registry.modelcontextprotocol.io (per repo README). Route: GitHub private security advisory (per repo SECURITY.md).

Title

OCI ownership validation skips label-match check when upstream OCI registry returns HTTP 429, letting any authenticated publisher bind their io.github.<user>/* namespace to OCI images they do not control.

Summary

internal/validators/registries/oci.go:104-119 fails open on http.StatusTooManyRequests: when the registry's anonymous fetch to the upstream OCI registry is rate-limited, ValidateOCI returns nil and the publish is accepted without ever running the io.modelcontextprotocol.server.name label-match check at lines 122-141. That label check is the only cross-system ownership proof the registry applies to OCI packages — every other registry type (NPM, PyPI, NuGet, MCPB) treats a non-200 upstream response as a hard error.

The fail-open trigger is attacker-controllable. The registry uses authn.Anonymous against Docker Hub, which is rate-limited to 100 manifest pulls per 6 hours per egress IP, and the production NGINX rate limit allows 180 publishes/minute (3 RPS, burst 540) per source IP. A single attacker from a single IP can exhaust the registry's shared anonymous quota in roughly 33 seconds, then submit a final publish that points packages[].identifier at a Docker Hub image they do not own. The validator hits the 429 fail-open branch, returns nil, and the registry stores a record under the attacker's namespace claiming the unrelated image as its package payload, with no label proof in evidence.

The fail-open is also reached without an attacker present. Docker Hub routinely 429s busy egress IPs during organic traffic, so publishes during those windows skip OCI ownership validation silently.

Vulnerable code

internal/validators/registries/oci.go:97-142:

img, err := remote.Image(ref, remote.WithAuth(authn.Anonymous), remote.WithContext(timeoutCtx))
if err != nil {
    if errors.Is(err, context.DeadlineExceeded) {
        return fmt.Errorf("OCI image validation timed out after 30 seconds for '%s'. The registry may be slow or unreachable", pkg.Identifier)
    }

    var transportErr *transport.Error
    if errors.As(err, &transportErr) {
        switch transportErr.StatusCode {
        case http.StatusTooManyRequests:
            // Rate limited - skip validation to avoid blocking publishers
            // This is intentional: we prioritize UX over strict validation during high traffic
            log.Printf("Skipping OCI validation for %s due to rate limiting", pkg.Identifier)
            return nil                                              // <-- FAIL-OPEN
        case http.StatusNotFound:
            return fmt.Errorf("OCI image '%s' does not exist in the registry", pkg.Identifier)
        case http.StatusUnauthorized, http.StatusForbidden:
            return fmt.Errorf("OCI image '%s' is private or requires authentication. Only public images are supported", pkg.Identifier)
        }
    }
    return fmt.Errorf("failed to fetch OCI image: %w", err)
}

// Get the image config which contains labels
configFile, err := img.ConfigFile()
if err != nil {
    return fmt.Errorf("failed to get image config: %w", err)
}

// Validate the MCP server name label
if configFile.Config.Labels == nil {
    return fmt.Errorf("OCI image '%s' is missing required annotation. Add this to your Dockerfile: LABEL io.modelcontextprotocol.server.name=\"%s\"", pkg.Identifier, serverName)
}

mcpName, exists := configFile.Config.Labels["io.modelcontextprotocol.server.name"]
if !exists {
    return fmt.Errorf("OCI image '%s' is missing…
Record
GHSA-2v5f-5r6w-p67r
CVSS 3.1
3.5 LowCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N
Weakness
CWE-636
Updated
2026-11-02
NVD 3.5

The MCP Registry provides MCP clients with a list of MCP servers, like an app store for MCP servers. Prior to 1.7.9, OCI ownership validation skips label-match check when upstream OCI registry returns HTTP 429, letting any authenticated publisher bind their io.github.<user>/* namespace to OCI images they do not control. internal/validators/registries/oci.go:104-119 fails open on http.StatusTooManyRequests: when the registry's anonymous fetch to the upstream OCI registry is rate-limited, ValidateOCI returns nil and the publish is accepted without ever running the io.modelcontextprotocol.server.name label-match check at lines 122-141. That label check is the only cross-system ownership proof the registry applies to OCI packages — every other registry type (NPM, PyPI, NuGet, MCPB) treats a non-200 upstream response as a hard error. This vulnerability is fixed in 1.7.9.

Record
CVE-2026-45781
CVSS 3.1
3.5 LowCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N
Weakness
CWE-636
Updated
2026-11-02
OSV 3.5

MCP Registry: OCI ownership validation fails open on upstream rate limits, allowing attacker-controlled package claims

The MCP Registry provides MCP clients with a list of MCP servers, like an app store for MCP servers. Prior to 1.7.9, OCI ownership validation skips label-match check when upstream OCI registry returns HTTP 429, letting any authenticated publisher bind their io.github.<user>/* namespace to OCI images they do not control. internal/validators/registries/oci.go:104-119 fails open on http.StatusTooManyRequests: when the registry's anonymous fetch to the upstream OCI registry is rate-limited, ValidateOCI returns nil and the publish is accepted without ever running the io.modelcontextprotocol.server.name label-match check at lines 122-141. That label check is the only cross-system ownership proof the registry applies to OCI packages — every other registry type (NPM, PyPI, NuGet, MCPB) treats a non-200 upstream response as a hard error. This vulnerability is fixed in 1.7.9.

Record
CVE-2026-45781
CVSS 3.1
3.5 LowCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N
Weakness
CWE-636
Updated
2026-11-02
OSVGHSA-2v5f-5r6w-p67r 3.5

MCP Registry: OCI validator skips ownership check on upstream rate limits

OCI ownership validation fails open on upstream rate limits, allowing attacker to claim arbitrary public OCI images under their own namespace

Severity: Low (re-scored post-triage; see Maintainer triage note below) Affected: modelcontextprotocol/registry main branch at commit fe0cb3b (current HEAD as of 2026-05-09). Live deployment: https://registry.modelcontextprotocol.io (per repo README). Route: GitHub private security advisory (per repo SECURITY.md).

Title

OCI ownership validation skips label-match check when upstream OCI registry returns HTTP 429, letting any authenticated publisher bind their io.github.<user>/* namespace to OCI images they do not control.

Summary

internal/validators/registries/oci.go:104-119 fails open on http.StatusTooManyRequests: when the registry's anonymous fetch to the upstream OCI registry is rate-limited, ValidateOCI returns nil and the publish is accepted without ever running the io.modelcontextprotocol.server.name label-match check at lines 122-141. That label check is the only cross-system ownership proof the registry applies to OCI packages — every other registry type (NPM, PyPI, NuGet, MCPB) treats a non-200 upstream response as a hard error.

The fail-open trigger is attacker-controllable. The registry uses authn.Anonymous against Docker Hub, which is rate-limited to 100 manifest pulls per 6 hours per egress IP, and the production NGINX rate limit allows 180 publishes/minute (3 RPS, burst 540) per source IP. A single attacker from a single IP can exhaust the registry's shared anonymous quota in roughly 33 seconds, then submit a final publish that points packages[].identifier at a Docker Hub image they do not own. The validator hits the 429 fail-open branch, returns nil, and the registry stores a record under the attacker's namespace claiming the unrelated image as its package payload, with no label proof in evidence.

The fail-open is also reached without an attacker present. Docker Hub routinely 429s busy egress IPs during organic traffic, so publishes during those windows skip OCI ownership validation silently.

Vulnerable code

internal/validators/registries/oci.go:97-142:

img, err := remote.Image(ref, remote.WithAuth(authn.Anonymous), remote.WithContext(timeoutCtx))
if err != nil {
    if errors.Is(err, context.DeadlineExceeded) {
        return fmt.Errorf("OCI image validation timed out after 30 seconds for '%s'. The registry may be slow or unreachable", pkg.Identifier)
    }

    var transportErr *transport.Error
    if errors.As(err, &transportErr) {
        switch transportErr.StatusCode {
        case http.StatusTooManyRequests:
            // Rate limited - skip validation to avoid blocking publishers
            // This is intentional: we prioritize UX over strict validation during high traffic
            log.Printf("Skipping OCI validation for %s due to rate limiting", pkg.Identifier)
            return nil                                              // <-- FAIL-OPEN
        case http.StatusNotFound:
            return fmt.Errorf("OCI image '%s' does not exist in the registry", pkg.Identifier)
        case http.StatusUnauthorized, http.StatusForbidden:
            return fmt.Errorf("OCI image '%s' is private or requires authentication. Only public images are supported", pkg.Identifier)
        }
    }
    return fmt.Errorf("failed to fetch OCI image: %w", err)
}

// Get the image config which contains labels
configFile, err := img.ConfigFile()
if err != nil {
    return fmt.Errorf("failed to get image config: %w", err)
}

// Validate the MCP server name label
if configFile.Config.Labels == nil {
    return fmt.Errorf("OCI image '%s' is missing required annotation. Add this to your Dockerfile: LABEL io.modelcontextprotocol.server.name=\"%s\"", pkg.Identifier, serverName)
}

mcpName, exists := configFile.Config.Labels["io.modelcontextprotocol.server.name"]
if !exists {
    return fmt.Errorf("OCI image '%s' is missing…
Record
GHSA-2v5f-5r6w-p67r
CVSS 3.1
3.5 LowCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N
Weakness
CWE-636
Updated
2026-11-02
OSVGO-2026-5008 No score

MCP Registry: OCI validator skips ownership check on upstream rate limits in github.com/modelcontextprotocol/registry

MCP Registry: OCI validator skips ownership check on upstream rate limits in github.com/modelcontextprotocol/registry

Record
GO-2026-5008
Updated
2026-11-02
OSVopenSUSE-SU-2026:21483-1 No score

Security update for govulncheck-vulndb

This update for govulncheck-vulndb fixes the following issues:

  • Update to version 0.0.20260723T184607 2026-07-23T18:46:07Z (jsc#PED-11136).

Go CVE Numbering Authority IDs added or updated with aliases:

  • GO-2026-4730 CVE-2026-33022 GHSA-cv4x-93xx-wgfj
  • GO-2026-4761 CVE-2026-33211 GHSA-j5q5-j9gm-2w5c
  • GO-2026-5102 CVE-2026-45021 GHSA-3vcp-chfh-f6r2
  • GO-2026-5272 CVE-2026-40938 GHSA-94jr-7pqp-xhcq
  • GO-2026-5486 CVE-2026-40924 GHSA-m2cx-gpqf-qf74
  • GO-2026-5542 CVE-2026-40090 GHSA-pj97-4p9w-gx3q
  • GO-2026-5630 CVE-2026-25542 GHSA-rmx9-2pp3-xhcr
  • GO-2026-5643 CVE-2026-40923 GHSA-rx35-6rhx-7858
  • GO-2026-5675 CVE-2026-41492 GHSA-vvf7-6rmr-m29q
  • GO-2026-5711 CVE-2026-40161 GHSA-wjxp-xrpv-xpff
  • GO-2026-5746 CVE-2026-41567 GHSA-x86f-5xw2-fm2r
  • GO-2026-5749 CVE-2026-41328 GHSA-x92x-px7w-4gx4
  • GO-2026-5837 CVE-2026-44840 GHSA-q2m9-6jp9-c6mc
  • GO-2026-5929 CVE-2026-44342 GHSA-26v7-h57m-gh9m
  • GO-2026-5930 CVE-2026-33655 GHSA-6qcr-qxgr-m7fv
  • GO-2026-5933 GHSA-3g4q-2f67-2gvh
  • GO-2026-5934 GHSA-59qp-cfj3-rp64
  • GO-2026-5935 GHSA-7856-g3gv-9wq8
  • GO-2026-5936 CVE-2026-53552 GHSA-26rh-24rg-j3vv
  • GO-2026-5937 CVE-2026-53508 GHSA-2jcc-mxv7-p3f9
  • GO-2026-5938 CVE-2026-53553 GHSA-4g5x-hcwm-82jw
  • GO-2026-5939 CVE-2026-10517 GHSA-698x-9w2p-7vvp
  • GO-2026-5940 CVE-2026-53572 GHSA-6w3m-4hhp-775q
  • GO-2026-5941 CVE-2026-53487 GHSA-gvhc-wv3v-7pf8
  • GO-2026-5942 CVE-2026-46600
  • GO-2026-5944 CVE-2026-50197 GHSA-659f-rgp5-w4wf
  • GO-2026-5945 CVE-2026-6815 GHSA-rmxx-v9rj-vpvg
  • GO-2026-5946 CVE-2026-52831 GHSA-v5px-423j-pf7p
  • GO-2026-5947 CVE-2026-53649 GHSA-xqhv-chqm-fhcc
  • GO-2026-5948 CVE-2026-50554 GHSA-588f-fvcv-xhvf
  • GO-2026-5949 CVE-2026-50553 GHSA-rqrh-8wpv-x7hh
  • GO-2026-5950 CVE-2026-53602 GHSA-339v-266x-79xr
  • GO-2026-5951 CVE-2026-10219 GHSA-6jm8-4fhr-5w64
  • GO-2026-5952 CVE-2026-49834 GHSA-9vcr-p3rj-q5q6
  • GO-2026-5953 CVE-2026-9094 GHSA-c9w5-qp6m-m395
  • GO-2026-5956 CVE-2026-55252 GHSA-h5g6-xmh4-hc37
  • GO-2026-5957 CVE-2026-54158 GHSA-5xfx-xj4h-5p7r
  • GO-2026-5958 CVE-2026-54068 GHSA-gcm7-57gf-953c
  • GO-2026-5959 CVE-2026-54072 GHSA-h29v-hj44-q8cv
  • GO-2026-5961 CVE-2026-54069 GHSA-hvr9-72v2-fff3
  • GO-2026-5962 CVE-2026-54088 GHSA-m93h-4hw7-5qcm
  • GO-2026-5963 CVE-2026-54067 GHSA-mvjr-vv3c-w4qv
  • GO-2026-5964 CVE-2026-54066 GHSA-p4m3-mgmm-c664
  • GO-2026-5965 CVE-2026-54070 GHSA-w7cg-whh7-xp28
  • GO-2026-5966 CVE-2026-54089 GHSA-xqp3-jq6g-x3qm
  • GO-2026-5967 CVE-2026-50551 GHSA-56mp-4f3v-fgj2
  • GO-2026-5968 CVE-2026-54174 GHSA-fpg8-7664-jc5q
  • GO-2026-5969 GHSA-g936-7jqj-mwv8
  • GO-2026-5970 CVE-2026-56852
  • GO-2026-5973 CVE-2026-54250 GHSA-jxr7-mqhw-9p98
  • GO-2026-5974 CVE-2026-44300 GHSA-wmj8-9953-vff5
  • GO-2026-5975 CVE-2026-50018 GHSA-42j2-w334-qxw7
  • GO-2026-5976 CVE-2026-50141 GHSA-g7mm-9vx7-jm7h
  • GO-2026-5977 CVE-2026-50013 GHSA-qrh4-p6v4-mrfg
  • GO-2026-5978 CVE-2026-50125 GHSA-qw5r-ppcg-f8rj
  • GO-2026-5979 CVE-2026-50006 GHSA-xrcf-6jh3-ggvx
  • GO-2026-5980 CVE-2026-50158 GHSA-2c7f-fxww-6w6c
  • GO-2026-5981 GHSA-mqxv-9rm6-w8qc
  • GO-2026-5982 GHSA-pqg7-v6wh-3pfp
  • GO-2026-5984 CVE-2026-53604 GHSA-2p2f-px33-4vv5
  • GO-2026-5985 GHSA-7rx3-5wx3-5v76
  • GO-2026-5986 CVE-2026-61699 GHSA-cm26-5974-52h8
  • GO-2026-5987 CVE-2026-55513 GHSA-g4x6-jcvr-9m3g
  • GO-2026-5988 CVE-2026-54628 GHSA-hwrq-8wxh-q4xv
  • GO-2026-5989 CVE-2026-55512 GHSA-m3cx-mwpg-32jg
  • GO-2026-5990 CVE-2026-54629 GHSA-mf78-3rpf-r784
  • GO-2026-5991 CVE-2026-53603 GHSA-q4vm-pq3q-8wgq
  • GO-2026-5992 CVE-2026-61549 GHSA-qf34-295c-26v8
  • GO-2026-5996 CVE-2026-54450 GHSA-pph6-vfjv-vpjw
  • GO-2026-5997 CVE-2026-54452 GHSA-xgch-x3mx-cm3c
  • GO-2026-5998 CVE-2026-54495 GHSA-398h-7f66-3h4p
  • GO-2026-5999 CVE-2026-10814 GHSA-jh6h-v6mp-h22v
  • GO-2026-6002 CVE-2026-58196 GHSA-pr64-jmmf-jp54
  • GO-2026-6003 CVE-2026-53714 GHSA-22xc-xg2r-9j7v
  • GO-2026-6004 CVE-2026-52833 GHSA-3v79-m2cg-89ww
  • GO-2026-6005 CVE-2026-53715 GHSA-8fv2-88gg-hm7q
  • GO-2026-6006 CVE-2026-53716 GHSA-cxpq-8v7q-cg56 *…
Record
openSUSE-SU-2026:21483-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
github.com/modelcontextprotocol/registry
Go
 before 1.7.9
1.7.9
govulncheck-vulndb
openSUSE:Leap 16.0
From an advisory covering 1734 CVEs
 before 0.0.20260723T184607-160000.1.1
0.0.20260723T184607-160000.1.1

History

History
RecordedChangedSources
affected, facts
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-45781 is a low vulnerability (CVSS 3.5) in Modelcontextprotocol Registry, published May 14, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.23%, the 14th percentile. Fixed in github.com/modelcontextprotocol/registry 1.7.9.

References

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