Bug 2567759 (CVE-2026-77463)

Summary: CVE-2026-77463 github.com/umputun/remark42: Remark42: Security control bypass via spoofed IP headers
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in Remark42. The application trusts client-supplied HTTP forwarding headers to determine the client's IP address without verifying that requests originate from a trusted proxy. A remote attacker can exploit this vulnerability by sending spoofed IP headers, allowing them to bypass IP-based rate limiting, circumvent voting restrictions, forge identities, and corrupt audit logs.
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Description OSIDB Bzimport 2026-11-05 22:23:56 UTC 
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.