Is there a public exploit for CVE-2026-77463?

No public exploit for CVE-2026-77463 was found in Exploit-DB, Metasploit, Nuclei templates or public proof-of-concept repositories. That is an absence of evidence rather than proof that none exists.

How severe is CVE-2026-77463?

CVE-2026-77463 scores CVSS 6.5 (v3.1), rated medium. EPSS puts the chance of exploitation in the next 30 days at 0.22%.

What does CVE-2026-77463 affect?

CVE-2026-77463 affects umputun github.com/umputun/remark42/backend, github.com/umputun/remark42.

6.5 Medium

Remark42: Rate limit bypass via unconditional trust of X-Forwarded-For/X-Real-IP headers in direct-internet deployment

CVE-2026-77463

Summary Remark42 applied chi's middleware.RealIP globally, trusting True-Client-IP / X-Real-IP / X-Forwarded-For headers without verifying the request came from a trusted proxy. The per-IP rate limiters key on the overwritten r.RemoteAddr, so any client can bypass every per-IP rate limiter by rotating spoofed IP headers. The same spoofed IP also drives other per-IP controls (stored comment IP, anonymous identity derivation, and --votes-ip vote de-duplication). This affects deployments reachable directly from the internet (Remark42's built-in HTTP, static TLS, and ACME modes are all documented and supported), as well as any proxied deployment where the proxy forwards an attacker-controlled recognised header. Details The router applies middleware.RealIP globally, ahead of the per-route limiters, without any check that the server is behind a trusted proxy (in v1.16.1, backend/app/rest/api/rest.go:207). The rateLimiter function (v1.16.1, backend/app/rest/api/rest.go:769-779) builds a tollbooth limiter with IPLookup{Name: "RemoteAddr"}, which reads r.RemoteAddr. Since chi's middleware.RealIP (v1.16.1, backend/vendor/github.com/go-chi/chi/v5/middleware/realip.go:42-55) unconditionally…

Assessment

CVSS: 6.5 (v3.1)
Severity: Medium
EPSS: 0.22% chance of exploitation in the next 30 days
Known exploited: Not listed in CISA KEV
Exploit availability: Nothing found in Exploit-DB, Metasploit, Nuclei or public PoC repositories
Published: 9 November 2026
Last updated: 9 November 2026
Affected: umputun · remark42 · github.com/umputun/remark42/backend · github.com/umputun/remark42
Weakness: CWE-348, CWE-807
Assigner: GitHub_M

CVSS vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

At the source

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