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Fencer Intel
medium 6.5

CVE-2026-77463 json

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

published 6d ago modified yesterday also EUVD-2026-117799 , GHSA-56x6-q882-mf27

cvss
6.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 12%
public exploits
0
none known

Summary

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.

Patch / fix

  • go github.com/umputun/remark42/backend 1.16.2
  • remark42 remark42 1.16.2

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CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
2d ago

Exploit prediction

0.22% chance of exploitation in the next 30 days, higher than 12% of all scored CVEs (FIRST EPSS, 2026-11-11).

Exploits and checks

  • github.com https://github.com/umputun/remark42/security/advisories/GHSA-56x6-q882-mf27 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
GitHub 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

Affected packages

ecosystem package affected fixed in
go github.com/umputun/remark42/backend
>=1.0.0, <1.16.2
1.16.2
go github.com/umputun/remark42
>=1.0.0, <=1.2.0
 no fix listed

Affected products

  • umputun remark42

Classification

Weakness
  • CWE-348 Use of Less Trusted Source
  • CWE-807 Reliance on Untrusted Inputs in a Security Decision

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.