umputun Remark42 up to 1.16.1 IP Handler middleware.RealIP True-Client-IP/X-Real-IP/X-Forwarded-For improper authentication

Summaryinfo

A vulnerability classified as critical has been found in umputun Remark42 up to 1.16.1. This affects the function middleware.RealIP of the component IP Handler. The manipulation of the argument True-Client-IP/X-Real-IP/X-Forwarded-For leads to improper authentication. This vulnerability is referenced as CVE-2026-77463. Remote exploitation of the attack is possible. No exploit is available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in umputun Remark42 up to 1.16.1. It has been rated as critical. This issue affects the function middleware.RealIP of the component IP Handler. The manipulation of the argument True-Client-IP/X-Real-IP/X-Forwarded-For with an unknown input leads to a improper authentication vulnerability. Using CWE to declare the problem leads to CWE-287. When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. Impacted is integrity, and availability. The summary by CVE is:

Remark42 is a self-hosted comment engine for blogs, articles, or any other place where readers can add comments. From 1.0.0 until 1.16.2, Remark42 globally trusts True-Client-IP, X-Real-IP, and X-Forwarded-For without verifying that the direct peer is a trusted proxy, and middleware.RealIP overwrites r.RemoteAddr before per-IP controls run. In a directly reachable deployment, or a proxy that forwards attacker-controlled headers, a remote attacker can rotate spoofed forwarding headers to obtain fresh token buckets for rate-limited endpoints, bypass vote de-duplication when --votes-ip is enabled, mint anonymous identities, and poison stored comment IPs and request logs. The global concurrent-request throttle and per-request timeouts still limit availability impact. Mitigation support is available in version 1.16.2, but operators must configure --trusted-proxy for the deployment topology.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-77463 since 08/20/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details of the vulnerability are known, but there is no available exploit.

Upgrading to version 1.16.2 eliminates this vulnerability.

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Productinfo

Vendor

• umputun

Name

• Remark42

Version

• 1.16.0
• 1.16.1

Website

• Product: https://github.com/umputun/remark42/

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