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Fencer Vulns
medium 5.3

CVE-2023-38492 json

Kirby vulnerable to denial of service from unlimited password lengths

published 2023-07-27 3 y ago modified 2026-09-10 1 mo ago also GHSA-3v6j-v3qc-cxff , EUVD-2023-1943

cvss
5.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.2%
EPSS 1.2% chance of exploitation in 30 days, percentile 67%
public exploits
0
none known

Summary

Kirby is a content management system. A vulnerability in versions prior to 3.5.8.3, 3.6.6.3, 3.7.5.2, 3.8.4.1, and 3.9.6 affects all Kirby sites with user accounts (unless Kirby's API and Panel are disabled in the config). The real-world impact of this vulnerability is limited, however we still recommend to update to one of the patch releases because they also fix more severe vulnerabilities.

Kirby's authentication endpoint did not limit the password length. This allowed attackers to provide a password with a length up to the server's maximum request body length. Validating that password against the user's actual password requires hashing the provided password, which requires more CPU and memory resources (and therefore processing time) the longer the provided password gets. This could be abused by an attacker to cause the website to become unresponsive or unavailable. Because Kirby comes with a built-in brute force protection, the impact of this vulnerability is limited to 10 failed logins from each IP address and 10 failed logins for each existing user per hour.

The problem has been patched in Kirby 3.5.8.3, 3.6.6.3, 3.7.5.2, 3.8.4.1, and 3.9.6. In all of the mentioned releases, the maintainers have added password length limits in the affected code so that passwords longer than 1000 bytes are immediately blocked, both when setting a password and when logging in.

Patch / fix

  • packagist getkirby/cms 3.5.8.3, 3.6.6.3, 3.7.5.2, 3.8.4.1, 3.9.6
  • getkirby kirby 3.5.8.3, 3.6.6.3, 3.7.5.2, 3.8.4.1, 3.9.6

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
2 y ago

Exploit prediction

1.18% chance of exploitation in the next 30 days, higher than 67% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
GitHub 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Affected packages

ecosystem package affected fixed in
packagist getkirby/cms
<3.5.8.3
>=3.6.0, <3.6.6.3
>=3.7.0, <3.7.5.2
>=3.8.0, <3.8.4.1
>=3.9.0, <3.9.6
3.5.8.3
3.6.6.3
3.7.5.2
3.8.4.1
3.9.6

Affected products

  • getkirby kirby

Classification

Weakness
  • CWE-770 Allocation of Resources Without Limits or Throttling

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.