Capgo: Client-Side Enforcement of Server-Side Security
CVE-2026-56256 is a high-severity client-side enforcement of server-side security vulnerability in Capgo, with a CVSS 3.1 base score of 7.1 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. The record lists version 12.128.2 as the first without the flaw, so updating Capgo to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.3% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Capgo to 12.128.2 or a later version.
- Read the advisory on github.com for workarounds and exact fixed builds.
Affected products and versions
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- LowSome restricted data can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:N. Scored by CNA (vulncheck.com).
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 7.1 | High | CNA (vulncheck.com) |
| CVSS 3.1 | 7.1 | High | CNA (vulncheck.com) |
Official description
Capgo before 12.128.2 enforces mandatory two-factor authentication only at the UI level. Sensitive Organization (ORG) management API endpoints (e.g., editing organization details, inviting users) do not validate 2FA completion on the backend. An authenticated Admin user who has not enabled 2FA can replay or modify a previously captured ORG API request to perform privileged organization actions, bypassing the globally enforced 2FA requirement.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Client-Side Enforcement of Server-Side Security
The product includes a server that relies on the client to implement a protection mechanism that is intended to protect the server.
How developers prevent this class of flaw
- If some degree of trust is required between the two entities, then use integrity checking and strong authentication to ensure that the inputs are coming from a trusted source. Design the product so that this trust is managed in a centralized fashion, especially if there are complex or numerous communication channels, in order to reduce the risks that the implementer will mistakenly omit a check in a single code path.
More Client-Side Enforcement of Server-Side Security vulnerabilities (CWE-602)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: poc, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Other references
Other vulnerabilities in Capgo
- 8.1 High severity
- 7.3 High severity
- 8.3 High severity
- 7.5 High severity
- 7.5 High severity
- 8.3 High severity
Recent Client-Side Enforcement of Server-Side Security vulnerabilities
- 8.8 High severity
- 8.3 High severity
- 8.8 High severity
- 8.1 High severity
- 7.3 High severity
- 10.0 Critical severity
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