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Fencer Vulns
critical 9.6

CVE-2026-55518 json

Avo: Missing Authorization in Avo Association Attach Endpoint Allows Unauthorized Relationship Manipulation and Privilege Escalation

published 2026-06-17 4 mo ago modified 2026-10-24 15 d ago also EUVD-2026-45334 , GHSA-8fq9-273g-6mrg

cvss
9.6
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 35%
public exploits
0
none known

Summary

Avo is a framework to create admin panels for Ruby on Rails apps. Prior to 3.32.1 and 4.0.0.beta.51, Avo's association attach workflow checks attach_<association>? in the UI and GET /resources/:resource/:id/:related/new path, but the actual write endpoint, POST /resources/:resource/:id/:related, does not run the same authorization check before mutating the association through Avo::AssociationsController#create. An authenticated low-privileged Avo user can bypass hidden or disabled attach controls and directly attach related records to a parent record by sending a crafted POST request, which can lead to privilege escalation and cross-tenant data exposure where associations represent authorization-bearing relationships. This issue is fixed in versions 3.32.1 and 4.0.0.beta.51.

Patch / fix

  • rubygems avo 3.32.1, 4.0.0.beta.51
  • avohq avo 3.32.1, 4.0.0.beta.51

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
total
Assessed
3 mo ago

Exploit prediction

0.41% chance of exploitation in the next 30 days, higher than 35% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/avo-hq/avo/security/advisories/GHSA-8fq9-273g-6mrg referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 9.6 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N
GitHub 3.1 9.6 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N

Affected packages

ecosystem package affected fixed in
rubygems avo
<3.32.1
>=4.0.0.beta.1, <4.0.0.beta.51
3.32.1
4.0.0.beta.51

Affected products

  • avo-hq avo

Classification

Weakness
  • CWE-639 Authorization Bypass Through User-Controlled Key
  • CWE-862 Missing Authorization
  • CWE-863 Incorrect Authorization

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.

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