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CVE-2026-42560

auth: Patreon provider assigns the same local user ID to every authenticated Patreon account, enabling cross‑user impersonation

9.1 CriticalFix available

auth provides authentication via oauth2, direct and email. From versions 1.18.0 to before 1.25.2 and 2.0.0 to before 2.1.2, the Patreon OAuth provider maps every authenticated Patreon account to the same local user.ID, instead of deriving a unique ID from the Patreon account returned by Patreon. In practice, this means all Patreon-authenticated users of an application using this library are collapsed into a single local identity. Any application that trusts token.User.ID as the stable account key can end up mixing or fully merging unrelated Patreon users, which can lead to cross-account access, privilege confusion, and subscription-state leakage. This issue has been patched in versions 1.25.2 and 2.1.2.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
None

Exploit likelihood

0.42%Up 0.3 points since May 9, 2026
90%50%10%1%

What each source reports

CVE List Score used 9.1

auth: Patreon provider assigns the same local user ID to every authenticated Patreon account, enabling cross‑user impersonation

auth provides authentication via oauth2, direct and email. From versions 1.18.0 to before 1.25.2 and 2.0.0 to before 2.1.2, the Patreon OAuth provider maps every authenticated Patreon account to the same local user.ID, instead of deriving a unique ID from the Patreon account returned by Patreon. In practice, this means all Patreon-authenticated users of an application using this library are collapsed into a single local identity. Any application that trusts token.User.ID as the stable account key can end up mixing or fully merging unrelated Patreon users, which can lead to cross-account access, privilege confusion, and subscription-state leakage. This issue has been patched in versions 1.25.2 and 2.1.2.

Record
CVE-2026-42560
CVSS 3.1
9.1 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-287
Updated
2026-11-02
EUVDEUVD-2026-28904 9.1

auth provides authentication via oauth2, direct and email. From versions 1.18.0 to before 1.25.2 and 2.0.0 to before 2.1.2, the Patreon OAuth provider maps every authenticated Patreon account to the same local user.ID, instead of deriving a unique ID from the Patreon account returned by Patreon. In practice, this means all Patreon-authenticated users of an application using this library are collapsed into a single local identity. Any application that trusts token.User.ID as the stable account key can end up mixing or fully merging unrelated Patreon users, which can lead to cross-account access, privilege confusion, and subscription-state leakage. This issue has been patched in versions 1.25.2 and 2.1.2.

Record
EUVD-2026-28904
CVSS 3.1
9.1 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-f6qq-3m3h-4g42 9.1

auth: Patreon provider assigns the same local user ID to every authenticated Patreon account, enabling cross‑user impersonation

Summary

The Patreon OAuth provider maps every authenticated Patreon account to the same local user.ID, instead of deriving a unique ID from the Patreon account returned by Patreon.

In practice, this means all Patreon-authenticated users of an application using this library are collapsed into a single local identity. Any application that trusts token.User.ID as the stable account key can end up mixing or fully merging unrelated Patreon users, which can lead to cross-account access, privilege confusion, and subscription-state leakage.

Details

The bug is in the Patreon provider's user-mapping logic.

Both the root module and the v2 module create a fresh empty token.User{} and then derive the Patreon ID from userInfo.ID before that field has been populated:

mapUser: func(data UserData, bdata []byte) token.User {
    userInfo := token.User{}

    uinfoJSON := uinfo{}
    if err := json.Unmarshal(bdata, &uinfoJSON); err == nil {
        userInfo.ID = "patreon_" + token.HashID(sha1.New(), userInfo.ID)
        userInfo.Name = uinfoJSON.Data.Attributes.FullName
        userInfo.Picture = uinfoJSON.Data.Attributes.ImageURL
        ...
    }
    return userInfo
}

Affected locations:

  • provider/providers.go:257
  • v2/provider/providers.go:257

At that point, userInfo.ID is still the empty string, so the effective result is always:

patreon_ + sha1("")

which is:

patreon_da39a3ee5e6b4b0d3255bfef95601890afd80709

for every Patreon user.

The code appears to have intended to hash the Patreon user ID returned by Patreon, i.e. uinfoJSON.Data.ID, but instead hashes the uninitialized destination field.

Why this matters:

  1. Patreon is a documented, supported provider.
  2. The library documents token.User.ID as the hashed user ID exposed to consumers.
  3. The OAuth flow stores the mapped user object in JWT claims, and middleware later injects that object into the request context verbatim, consuming handlers receive the provider's wrong user.ID as authoritative identity.

Relevant flow in v2:

  • v2/provider/oauth2.go:207 calls u := p.mapUser(...)
  • v2/provider/oauth2.go:223 stores u in token claims
  • v2/middleware/auth.go:154 copies *claims.User into request context

The existing tests already encode the broken behavior:

  • provider/providers_test.go:179
  • provider/providers_test.go:204
  • v2/provider/providers_test.go:179
  • v2/provider/providers_test.go:204

Those tests assert the constant empty-string hash value for Patreon users.

PoC

This can be reproduced locally without contacting Patreon by exercising the provider's mapUser logic with two different Patreon payloads.

From the repository root, create a temporary test file:

v2/provider/patreon_repro_test.go

package provider

import "testing"

func TestPatreonSharedIdentity(t *testing.T) {
    r := NewPatreon(Params{
        URL:     "http://example.com",
        Cid:     "cid",
        Csecret: "secret",
    })

    a := r.mapUser(UserData{}, []byte(`{
        "data": {
            "attributes": {
                "full_name": "Alice",
                "image_url": "https://example.com/alice.png"
            },
            "id": "1111111"
        }
    }`))

    b := r.mapUser(UserData{}, []byte(`{
        "data": {
            "attributes": {
                "full_name": "Bob",
                "image_url": "https://example.com/bob.png"
            },
            "id": "9999999"
        }
    }`))

    if a.ID != b.ID {
        t.Fatalf("expected IDs to collide, got %q and %q", a.ID, b.ID)
    }

    t.Logf("Alice -> %s", a.ID)
    t.Logf("Bob   -> %s", b.ID)
}

Then run:

cd v2
go test ./provider -run TestPatreonSharedIdentity -v

Expected result:

Alice -> patreon_da39a3ee5e6b4b0d3255bfef95601890afd80709
Bob   -> patreon_da39a3ee5e6b4b0d3255bfef95601890afd80709

I also confirmed this locally with three distinct Patreon data.id values; all of them produced the…

Record
GHSA-f6qq-3m3h-4g42
CVSS 3.1
9.1 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-287
Updated
2026-11-02
NVD 9.1

auth provides authentication via oauth2, direct and email. From versions 1.18.0 to before 1.25.2 and 2.0.0 to before 2.1.2, the Patreon OAuth provider maps every authenticated Patreon account to the same local user.ID, instead of deriving a unique ID from the Patreon account returned by Patreon. In practice, this means all Patreon-authenticated users of an application using this library are collapsed into a single local identity. Any application that trusts token.User.ID as the stable account key can end up mixing or fully merging unrelated Patreon users, which can lead to cross-account access, privilege confusion, and subscription-state leakage. This issue has been patched in versions 1.25.2 and 2.1.2.

Record
CVE-2026-42560
CVSS 3.1
9.1 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-287
Updated
2026-11-02
OSV 9.1

auth: Patreon provider assigns the same local user ID to every authenticated Patreon account, enabling cross‑user impersonation

auth provides authentication via oauth2, direct and email. From versions 1.18.0 to before 1.25.2 and 2.0.0 to before 2.1.2, the Patreon OAuth provider maps every authenticated Patreon account to the same local user.ID, instead of deriving a unique ID from the Patreon account returned by Patreon. In practice, this means all Patreon-authenticated users of an application using this library are collapsed into a single local identity. Any application that trusts token.User.ID as the stable account key can end up mixing or fully merging unrelated Patreon users, which can lead to cross-account access, privilege confusion, and subscription-state leakage. This issue has been patched in versions 1.25.2 and 2.1.2.

Record
CVE-2026-42560
CVSS 3.1
9.1 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-287
Updated
2026-11-02
OSVGHSA-f6qq-3m3h-4g42 9.1

auth: Patreon provider assigns the same local user ID to every authenticated Patreon account, enabling cross‑user impersonation

Summary

The Patreon OAuth provider maps every authenticated Patreon account to the same local user.ID, instead of deriving a unique ID from the Patreon account returned by Patreon.

In practice, this means all Patreon-authenticated users of an application using this library are collapsed into a single local identity. Any application that trusts token.User.ID as the stable account key can end up mixing or fully merging unrelated Patreon users, which can lead to cross-account access, privilege confusion, and subscription-state leakage.

Details

The bug is in the Patreon provider's user-mapping logic.

Both the root module and the v2 module create a fresh empty token.User{} and then derive the Patreon ID from userInfo.ID before that field has been populated:

mapUser: func(data UserData, bdata []byte) token.User {
    userInfo := token.User{}

    uinfoJSON := uinfo{}
    if err := json.Unmarshal(bdata, &uinfoJSON); err == nil {
        userInfo.ID = "patreon_" + token.HashID(sha1.New(), userInfo.ID)
        userInfo.Name = uinfoJSON.Data.Attributes.FullName
        userInfo.Picture = uinfoJSON.Data.Attributes.ImageURL
        ...
    }
    return userInfo
}

Affected locations:

  • provider/providers.go:257
  • v2/provider/providers.go:257

At that point, userInfo.ID is still the empty string, so the effective result is always:

patreon_ + sha1("")

which is:

patreon_da39a3ee5e6b4b0d3255bfef95601890afd80709

for every Patreon user.

The code appears to have intended to hash the Patreon user ID returned by Patreon, i.e. uinfoJSON.Data.ID, but instead hashes the uninitialized destination field.

Why this matters:

  1. Patreon is a documented, supported provider.
  2. The library documents token.User.ID as the hashed user ID exposed to consumers.
  3. The OAuth flow stores the mapped user object in JWT claims, and middleware later injects that object into the request context verbatim, consuming handlers receive the provider's wrong user.ID as authoritative identity.

Relevant flow in v2:

  • v2/provider/oauth2.go:207 calls u := p.mapUser(...)
  • v2/provider/oauth2.go:223 stores u in token claims
  • v2/middleware/auth.go:154 copies *claims.User into request context

The existing tests already encode the broken behavior:

  • provider/providers_test.go:179
  • provider/providers_test.go:204
  • v2/provider/providers_test.go:179
  • v2/provider/providers_test.go:204

Those tests assert the constant empty-string hash value for Patreon users.

PoC

This can be reproduced locally without contacting Patreon by exercising the provider's mapUser logic with two different Patreon payloads.

From the repository root, create a temporary test file:

v2/provider/patreon_repro_test.go

package provider

import "testing"

func TestPatreonSharedIdentity(t *testing.T) {
    r := NewPatreon(Params{
        URL:     "http://example.com",
        Cid:     "cid",
        Csecret: "secret",
    })

    a := r.mapUser(UserData{}, []byte(`{
        "data": {
            "attributes": {
                "full_name": "Alice",
                "image_url": "https://example.com/alice.png"
            },
            "id": "1111111"
        }
    }`))

    b := r.mapUser(UserData{}, []byte(`{
        "data": {
            "attributes": {
                "full_name": "Bob",
                "image_url": "https://example.com/bob.png"
            },
            "id": "9999999"
        }
    }`))

    if a.ID != b.ID {
        t.Fatalf("expected IDs to collide, got %q and %q", a.ID, b.ID)
    }

    t.Logf("Alice -> %s", a.ID)
    t.Logf("Bob   -> %s", b.ID)
}

Then run:

cd v2
go test ./provider -run TestPatreonSharedIdentity -v

Expected result:

Alice -> patreon_da39a3ee5e6b4b0d3255bfef95601890afd80709
Bob   -> patreon_da39a3ee5e6b4b0d3255bfef95601890afd80709

I also confirmed this locally with three distinct Patreon data.id values; all of them produced the…

Record
GHSA-f6qq-3m3h-4g42
CVSS 3.1
9.1 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-287
Updated
2026-11-02
OSVGO-2026-5348 No score

auth: Patreon provider assigns the same local user ID to every authenticated Patreon account, enabling cross‑user impersonation in github.com/go-pkgz/auth

auth: Patreon provider assigns the same local user ID to every authenticated Patreon account, enabling cross‑user impersonation in github.com/go-pkgz/auth

Record
GO-2026-5348
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/go-pkgz/auth
Go
 1.18.0 to 1.25.1
1.25.2
github.com/go-pkgz/auth/v2
Go
 2.0.0 to 2.1.1
2.1.2
github.com/go-pkgz/auth
Go
 1.18.0 up to 1.25.2
1.25.2
github.com/go-pkgz/auth/v2
Go
 2.0.0 up to 2.1.2
2.1.2
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-2026-42560 is a critical vulnerability (CVSS 9.1) in Go-pkgz Auth, published April 30, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.42%, the 36th percentile. Fixed in github.com/go-pkgz/auth 1.25.2.

References

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Left out here: 1,542 references and the rest of 3 source descriptions. The JSON record has them.

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