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Fencer Vulns
medium 5.9

CVE-2026-75514 json

BunkerWeb: rDNS bypass via missing forward-confirmation (FCrDNS) in blacklist, greylist, and antibot

published 2026-08-20 2 mo ago modified 2026-10-18 21 d ago also EUVD-2026-63542

cvss
5.9
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 48%
public exploits
0
none known

Summary

BunkerWeb is an open-source, next-generation Web Application Firewall. Prior to 1.6.13, the blacklist, greylist, and antibot modules in src/common/core/blacklist/blacklist.lua, src/common/core/greylist/greylist.lua, and src/common/core/antibot/antibot.lua trust PTR suffix matches in IGNORE_RDNS, GREYLIST_RDNS, and ANTIBOT_IGNORE_RDNS without using get_ips to confirm that the hostname resolves to the client address. An unauthenticated remote attacker who controls a PTR record can spoof a trusted suffix to bypass rDNS-based blacklisting, gain greylist treatment, or skip an antibot challenge. This issue is fixed in version 1.6.13.

Patch / fix

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
2 mo ago

Exploit prediction

0.60% chance of exploitation in the next 30 days, higher than 48% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/bunkerity/bunkerweb/security/advisories/GHSA-q54j-5484-pvjm referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

Affected products

  • bunkerity bunkerweb

Classification

Weakness
  • CWE-350 Reliance on Reverse DNS Resolution for a Security-Critical Action

References

Sources

Fencer Vulns 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.