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Fencer Intel
critical 9.1

CVE-2026-88864 json

Capgo SSO Provider Authentication Bypass via PostgREST Direct Write

published 2mo ago modified last mo. also EUVD-2026-75414 , GHSA-xg7v-83qv-qfff

Unreviewed: the maintainers' own advisory

Published by the maintainers on their GitHub repository Cap-go/capgo.app. GitHub has not reviewed it into the GitHub Advisory Database, so the affected packages and versions are the maintainers' word. Read the full advisory on GitHub.

cvss
9.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 30%
public exploits
0
none known

Summary

Capgo (capgo.app) fails to restrict direct write access to the public.sso_providers table exposed through Supabase PostgREST. A holder of an ordinary Capgo full API key can insert a row with status='active' and enforce_sso=true, bypassing the intended backend SSO provisioning route (supabase/functions/_backend/private/sso/providers.ts) and its controls: the Enterprise plan requirement, SSO provider creation via the Supabase Management API, DNS TXT domain-ownership verification, the pending_verification → verified → active status transition, and issuance of a trusted provider ID by Supabase Auth. The forged row is trusted by SSO discovery and enforcement logic, including the unauthenticated login preflight endpoint /private/sso/check-domain, which then reports {"has_sso": true, "enforce_sso": true} for domains that were never verified, allowing attacker-controlled SSO enforcement to be asserted for arbitrary domains and disrupting normal login. All versions are affected; at the time of the advisory no patch was available.

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CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
total
Assessed
2mo ago

Exploit prediction

0.37% chance of exploitation in the next 30 days, higher than 30% of all scored CVEs (FIRST EPSS, 2026-11-11).

Exploits and checks

  • github.com https://github.com/Cap-go/capgo.app/security/advisories/GHSA-xg7v-83qv-qfff referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 9.3 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CNA 3.1 9.1 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:H/A:L
CNA 4.0 9.3 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/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

Affected products

  • Cap-go capgo.app

Classification

Weakness

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

The maintainers of Cap-go/capgo.app published their own advisory on GitHub. Reviewed sources take precedence over it.