CVE-2026-77130: SYSSY JWT Token Auth Bypass Vulnerability

CVE-2026-77130 Overview

CVE-2026-77130 is a session expiration flaw in a TYPO3 extension that fails to validate the expiration claim of client-supplied JSON Web Tokens (JWTs). An attacker who already controls a valid SYSSY project API key can present an expired JWT and still authenticate successfully. The weakness is classified under CWE-613: Insufficient Session Expiration and is documented in the TYPO3 Security Advisory 2026-015. Exploitation is limited by the prerequisite that the attacker must already possess a valid API key for the affected project.

Critical Impact
An attacker with a valid API key can bypass JWT lifetime controls, extending session validity indefinitely and undermining token revocation guarantees.

Affected Products

TYPO3 SYSSY project extension (see TYPO3 Security Advisory 2026-015)
Specific affected versions are not enumerated in the NVD record
Refer to the vendor advisory for version-specific guidance

Discovery Timeline

2026-08-25 - CVE-2026-77130 published to NVD
2026-08-26 - Last updated in NVD database

Technical Details for CVE-2026-77130

Vulnerability Analysis

The vulnerability is a session management flaw in the JWT authentication path of the affected TYPO3 extension. JWTs carry an exp claim that defines the time after which the token must be rejected. The extension accepts tokens without enforcing this claim, so tokens remain usable past their intended lifetime.

This breaks a core assumption of stateless bearer-token authentication. Rotating or short-lived tokens no longer limit the exposure window when a token is captured or reused. The impact is bounded: exploitation requires possession of a valid API key for the SYSSY project, which places this in the category of privilege retention rather than initial access.

Root Cause

The extension's token verification routine omits the exp claim check during signature validation. The token's cryptographic integrity is verified, but its temporal validity is not. This mirrors the [CWE-613] pattern where session lifetime controls exist in the protocol but are not enforced by the server.

Attack Vector

The attack proceeds over the network against the extension's authenticated API surface. An attacker holding a valid SYSSY API key submits an expired JWT alongside the API key. The extension validates the signature, skips the expiration check, and grants access. Refer to the TYPO3 Security Advisory 2026-015 for the specific request paths and version details.

No verified exploit code is publicly available for this issue.

Detection Methods for CVE-2026-77130

Indicators of Compromise

API requests containing JWTs whose exp claim precedes the request timestamp
Authentication events tied to API keys whose associated tokens were previously marked expired or rotated
Anomalous session continuity across expected token rotation boundaries

Detection Strategies

Parse JWTs from application access logs and compare the exp claim against the request time, alerting on any accepted token where exp < now
Correlate API key usage with token issuance records to flag reuse of tokens past their issued lifetime
Baseline normal token lifetimes for the SYSSY extension and alert on outliers

Monitoring Recommendations

Forward TYPO3 and reverse-proxy access logs to a centralized analytics pipeline for JWT claim inspection
Monitor for repeated authentication attempts from a single API key using varying token payloads
Track administrative and API activity performed under long-lived sessions for post-hoc review

How to Mitigate CVE-2026-77130

Immediate Actions Required

Apply the fixed extension version referenced in TYPO3 Security Advisory 2026-015
Rotate any SYSSY project API keys that may have been exposed or shared
Invalidate outstanding JWTs issued by the affected extension and force reissuance

Patch Information

The vendor has published guidance in TYPO3 Security Advisory 2026-015. Administrators should upgrade the SYSSY extension to the fixed release identified in that advisory. Version-specific fix data is not included in the NVD record and must be sourced from the advisory.

Workarounds

Restrict access to the extension's API endpoints to trusted network ranges using a web application firewall or reverse-proxy allowlist
Enforce short API key rotation cycles until the patched extension is deployed
Reject requests at the proxy layer when the embedded JWT exp claim is in the past

bash

# Example nginx snippet to restrict SYSSY API access to a trusted CIDR
location /api/syssy/ {
    allow 10.0.0.0/24;
    deny all;
    proxy_pass http://typo3_backend;
}