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CVE-2026-44428

MCP Registry: GitHub OIDC tokens replayable across registry deployments due to shared audience

2.1 LowFix available

The MCP Registry provides MCP clients with a list of MCP servers, like an app store for MCP servers. Prior to 1.7.6, the client-side and server-side GitHub OIDC flow is bound only to a global audience string, not to the specific registry instance being targeted. On the client side, the publisher always appends audience=mcp-registry when requesting the GitHub Actions ID token, regardless of the selected --registry URL. On the server side, the exchange endpoint validates only that same fixed audience and then derives publish permissions directly from repository_owner. As a result, a token legitimately obtained while interacting with one registry deployment remains acceptable to any other deployment that shares the same code and audience string. This vulnerability is fixed in 1.7.6.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
Active

What an attacker can affect

Confidentiality
None
Integrity
Low
Availability
None

Exploit likelihood

0.22%Up 0.2 points since May 15, 2026
90%50%10%1%

What each source reports

CVE List Score used 2.1

MCP Registry: GitHub OIDC tokens replayable across registry deployments due to shared audience

The MCP Registry provides MCP clients with a list of MCP servers, like an app store for MCP servers. Prior to 1.7.6, the client-side and server-side GitHub OIDC flow is bound only to a global audience string, not to the specific registry instance being targeted. On the client side, the publisher always appends audience=mcp-registry when requesting the GitHub Actions ID token, regardless of the selected --registry URL. On the server side, the exchange endpoint validates only that same fixed audience and then derives publish permissions directly from repository_owner. As a result, a token legitimately obtained while interacting with one registry deployment remains acceptable to any other deployment that shares the same code and audience string. This vulnerability is fixed in 1.7.6.

Record
CVE-2026-44428
CVSS 4.0
2.1 LowCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N
Weakness
CWE-918
Updated
2026-11-02
EUVDEUVD-2026-30493 2.1

The MCP Registry provides MCP clients with a list of MCP servers, like an app store for MCP servers. Prior to 1.7.6, the client-side and server-side GitHub OIDC flow is bound only to a global audience string, not to the specific registry instance being targeted. On the client side, the publisher always appends audience=mcp-registry when requesting the GitHub Actions ID token, regardless of the selected --registry URL. On the server side, the exchange endpoint validates only that same fixed audience and then derives publish permissions directly from repository_owner. As a result, a token legitimately obtained while interacting with one registry deployment remains acceptable to any other deployment that shares the same code and audience string. This vulnerability is fixed in 1.7.6.

Record
EUVD-2026-30493
CVSS 4.0
2.1 LowCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-95c3-6vvw-4mrq 2.1

MCP Registry's GitHub OIDC tokens are replayable across registry deployments due to shared audience

[SECURITY] registry_001 Vulnerability Report

While analyzing the code logic, an area that may lead to unintended behavior under specific conditions was discovered.

Overview

  • Verified Version: c5c4b9e8890dd5754bee889b2f1417f4fe3b5ce5
  • Vulnerability Type: Authentication bypass via cross-registry OIDC token replay
  • Affected Location: cmd/publisher/commands/login.go:67-105,130-135,199-224; cmd/publisher/auth/github-oidc.go:24-38,58-75,108-165; internal/api/handlers/v0/auth/github_oidc.go:75-135,229-277,280-296
  • Trigger Scenario: a workflow invokes mcp-publisher login github-oidc --registry <other-registry> (or equivalent publish flow) and the publisher still requests a GitHub Actions ID token with the shared audience mcp-registry; any other registry deployment running this code can replay that token to its own /v0/auth/github-oidc endpoint and mint a publish-capable registry JWT for the same GitHub owner namespace.

Root Cause

The client-side and server-side GitHub OIDC flow is bound only to a global audience string, not to the specific registry instance being targeted. On the client side, the publisher always appends audience=mcp-registry when requesting the GitHub Actions ID token, regardless of the selected --registry URL. On the server side, the exchange endpoint validates only that same fixed audience and then derives publish permissions directly from repository_owner. As a result, a token legitimately obtained while interacting with one registry deployment remains acceptable to any other deployment that shares the same code and audience string.

Source-to-Sink Chain

  1. Source cmd/publisher/commands/login.go:67-105,130-135,199-224 parses the user-controlled --registry flag into flags.RegistryURL, creates a GitHubOIDCProvider, and calls authProvider.GetToken(ctx) for the chosen authentication method.
  2. Propagation cmd/publisher/auth/github-oidc.go:24-38 obtains an OIDC token and immediately exchanges it against the selected registry URL. cmd/publisher/auth/github-oidc.go:58-75 builds exchangeURL := o.registryURL + "/v0/auth/github-oidc" and posts the GitHub token to whichever registry instance was selected. cmd/publisher/auth/github-oidc.go:108-165 constructs fullURL := requestURL + "&audience=mcp-registry" and therefore requests the same audience for every registry deployment.
  3. Sink internal/api/handlers/v0/auth/github_oidc.go:75-135 validates only the shared audience value passed into ValidateToken. internal/api/handlers/v0/auth/github_oidc.go:254-277 calls h.validator.ValidateToken(ctx, oidcToken, "mcp-registry") and, on success, signs a new registry JWT. internal/api/handlers/v0/auth/github_oidc.go:280-296 converts claims.RepositoryOwner into the publish permission pattern io.github.<owner>/*, which is then embedded into the new registry JWT.

Exploitation Preconditions

  1. The victim uses the GitHub Actions OIDC publishing path.
  2. The victim workflow targets another registry deployment first, such as staging, self-hosted infrastructure, or an attacker-controlled registry URL.
  3. The receiving registry deployment can observe the posted OIDC token and replay it before expiry to another registry deployment running the same shared audience configuration.

Risk

This breaks deployment isolation between registry instances. A token issued for one registry interaction can be replayed across trust boundaries, allowing one deployment to impersonate the same GitHub owner identity on another deployment.

Impact

An attacker-controlled or compromised registry deployment can mint a valid registry JWT on another deployment and inherit publish permissions for the victim GitHub owner namespace. In practical terms, this enables unauthorized publication or update actions for names such as io.github.<owner>/* on the victim registry instance.

Remediation

  1. Replace the shared audience string with a registry-specific audience, such as…
Record
GHSA-95c3-6vvw-4mrq
CVSS 4.0
2.1 LowCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N
CVSS 3.1
4.7 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N
Weakness
CWE-918
Updated
2026-11-02
NVD 2.1

The MCP Registry provides MCP clients with a list of MCP servers, like an app store for MCP servers. Prior to 1.7.6, the client-side and server-side GitHub OIDC flow is bound only to a global audience string, not to the specific registry instance being targeted. On the client side, the publisher always appends audience=mcp-registry when requesting the GitHub Actions ID token, regardless of the selected --registry URL. On the server side, the exchange endpoint validates only that same fixed audience and then derives publish permissions directly from repository_owner. As a result, a token legitimately obtained while interacting with one registry deployment remains acceptable to any other deployment that shares the same code and audience string. This vulnerability is fixed in 1.7.6.

Record
CVE-2026-44428
CVSS 4.0
2.1 LowCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1
4.7 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N
Weakness
CWE-918
Updated
2026-11-02
OSV 2.1

MCP Registry: GitHub OIDC tokens replayable across registry deployments due to shared audience

The MCP Registry provides MCP clients with a list of MCP servers, like an app store for MCP servers. Prior to 1.7.6, the client-side and server-side GitHub OIDC flow is bound only to a global audience string, not to the specific registry instance being targeted. On the client side, the publisher always appends audience=mcp-registry when requesting the GitHub Actions ID token, regardless of the selected --registry URL. On the server side, the exchange endpoint validates only that same fixed audience and then derives publish permissions directly from repository_owner. As a result, a token legitimately obtained while interacting with one registry deployment remains acceptable to any other deployment that shares the same code and audience string. This vulnerability is fixed in 1.7.6.

Record
CVE-2026-44428
CVSS 4.0
2.1 LowCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N
Weakness
CWE-918
Updated
2026-11-02
OSVGHSA-95c3-6vvw-4mrq 2.1

MCP Registry's GitHub OIDC tokens are replayable across registry deployments due to shared audience

[SECURITY] registry_001 Vulnerability Report

While analyzing the code logic, an area that may lead to unintended behavior under specific conditions was discovered.

Overview

  • Verified Version: c5c4b9e8890dd5754bee889b2f1417f4fe3b5ce5
  • Vulnerability Type: Authentication bypass via cross-registry OIDC token replay
  • Affected Location: cmd/publisher/commands/login.go:67-105,130-135,199-224; cmd/publisher/auth/github-oidc.go:24-38,58-75,108-165; internal/api/handlers/v0/auth/github_oidc.go:75-135,229-277,280-296
  • Trigger Scenario: a workflow invokes mcp-publisher login github-oidc --registry <other-registry> (or equivalent publish flow) and the publisher still requests a GitHub Actions ID token with the shared audience mcp-registry; any other registry deployment running this code can replay that token to its own /v0/auth/github-oidc endpoint and mint a publish-capable registry JWT for the same GitHub owner namespace.

Root Cause

The client-side and server-side GitHub OIDC flow is bound only to a global audience string, not to the specific registry instance being targeted. On the client side, the publisher always appends audience=mcp-registry when requesting the GitHub Actions ID token, regardless of the selected --registry URL. On the server side, the exchange endpoint validates only that same fixed audience and then derives publish permissions directly from repository_owner. As a result, a token legitimately obtained while interacting with one registry deployment remains acceptable to any other deployment that shares the same code and audience string.

Source-to-Sink Chain

  1. Source cmd/publisher/commands/login.go:67-105,130-135,199-224 parses the user-controlled --registry flag into flags.RegistryURL, creates a GitHubOIDCProvider, and calls authProvider.GetToken(ctx) for the chosen authentication method.
  2. Propagation cmd/publisher/auth/github-oidc.go:24-38 obtains an OIDC token and immediately exchanges it against the selected registry URL. cmd/publisher/auth/github-oidc.go:58-75 builds exchangeURL := o.registryURL + "/v0/auth/github-oidc" and posts the GitHub token to whichever registry instance was selected. cmd/publisher/auth/github-oidc.go:108-165 constructs fullURL := requestURL + "&audience=mcp-registry" and therefore requests the same audience for every registry deployment.
  3. Sink internal/api/handlers/v0/auth/github_oidc.go:75-135 validates only the shared audience value passed into ValidateToken. internal/api/handlers/v0/auth/github_oidc.go:254-277 calls h.validator.ValidateToken(ctx, oidcToken, "mcp-registry") and, on success, signs a new registry JWT. internal/api/handlers/v0/auth/github_oidc.go:280-296 converts claims.RepositoryOwner into the publish permission pattern io.github.<owner>/*, which is then embedded into the new registry JWT.

Exploitation Preconditions

  1. The victim uses the GitHub Actions OIDC publishing path.
  2. The victim workflow targets another registry deployment first, such as staging, self-hosted infrastructure, or an attacker-controlled registry URL.
  3. The receiving registry deployment can observe the posted OIDC token and replay it before expiry to another registry deployment running the same shared audience configuration.

Risk

This breaks deployment isolation between registry instances. A token issued for one registry interaction can be replayed across trust boundaries, allowing one deployment to impersonate the same GitHub owner identity on another deployment.

Impact

An attacker-controlled or compromised registry deployment can mint a valid registry JWT on another deployment and inherit publish permissions for the victim GitHub owner namespace. In practical terms, this enables unauthorized publication or update actions for names such as io.github.<owner>/* on the victim registry instance.

Remediation

  1. Replace the shared audience string with a registry-specific audience, such as…
Record
GHSA-95c3-6vvw-4mrq
CVSS 4.0
2.1 LowCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N
CVSS 3.1
4.7 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N
Weakness
CWE-918
Updated
2026-11-02
OSVGO-2026-5273 No score

MCP Registry's GitHub OIDC tokens are replayable across registry deployments due to shared audience in github.com/modelcontextprotocol/registry

MCP Registry's GitHub OIDC tokens are replayable across registry deployments due to shared audience in github.com/modelcontextprotocol/registry

Record
GO-2026-5273
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 1.7.6
1.7.6
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-2026-44428 is a low vulnerability (CVSS 2.1) in Lfprojects Mcp Registry, published May 8, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.22%, the 12th percentile. Fixed in github.com/modelcontextprotocol/registry 1.7.6.

References

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