VULNpocalypse

CVE-2026-55872: GYM One admin user list is vulnerable to stored cross-site scripting

Advisory generated from the CVE record, CISA, Exploit Observer and VEDAS: what it is, whether it is exploited, who is affected, and how to fix and detect it.

Generated by VEDAS. Scores as of 2026-11-01 19:19 UTC. Rebuilt every few hours from cve-scores, CISA KEV and vedas-signatures. How this works and its limits.

What it is

GYM One is open-source gym management software for fitness centers, personal trainers, and sports clubs. Prior to 1.4.1, GYM One’s admin/users/index.php renders the stored firstname, lastname, and email profile fields into the administrator user list without HTML output encoding. An attacker who can store values in those fields can cause content to execute in an administrator’s browser when the administrator visits /admin/users/. The persistent script can access administrator-session data or perform actions with the administrator’s privileges until the stored record is removed. This issue is fixed in version 1.4.1.

Description quoted from the CVE record (assigned by GitHub_M, published 2026-10-15).

Weakness: CWE-79: Improper Neutralization of Input During Web Page Generation (‘Cross-site Scripting’)

How it can be exploited

Exploitable over the network with low attack complexity needing low privileges and a user must take an action. Impact: confidentiality high, integrity high, availability none. CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N

CISA assessment (SSVC): CISA assesses that a public proof of concept exists. Automatable: no. Technical impact: total.

Public exploit evidence (Exploit Observer)

Also known as: EUVD-2026-102308

VEDAS cluster: VEDAS:DOLPHINBABY

Exploit Observer links 3 pieces of public exploit code or detection modules that name this CVE or one of its aliases.

Exploit code and modules (3)

Code that names this CVE. A repository can be a working exploit, a scanner, a fake or malware; read it before running anything.

Vulnerability databases and vendor advisories (2)

Catalogue entries, not exploit evidence.

2 more references returned by Exploit Observer did not name this CVE or an alias, so they are left out.

VEDAS data as of 2026-11-01T17:12 UTC; fetched 2026-11-02.

Live scores

EPSS
0.003
low predicted chance of attack
VEDAS
0.987
strong exploit evidence
On CISA KEV
Not listed
Detection rule
Suricata

Who is affected

ProductAffectedNot affected
mayerbalintdev GYM-Oneversion < 1.4.1Not stated

Version ranges exactly as the CVE record states them. “Before X” means X is the first fixed version.

How to fix it

No fixed version or vendor advisory is listed in the CVE record yet. Watch the vendor’s security page.

How to detect it

Suricata rules (network detection)

1 rule that alert on traffic matching this exploit: VEDAS CVE-2026-55872 GYM One - Stored XSS via Profile Fields. Add them to your Suricata rule set and reload.

Show the rules
suricata
alert http $EXTERNAL_NET any -> $HTTP_SERVERS $HTTP_PORTS (msg:"VEDAS CVE-2026-55872 GYM One - Stored XSS via Profile Fields"; flow:established,to_server; http.method; content:"POST"; http.uri; content:"/register"; nocase; http.request_body; content:"firstname"; nocase; content:"<script"; nocase; fast_pattern; classtype:web-application-attack; reference:cve,CVE-2026-55872; reference:url,https://www.exploit.observer/?keyword=CVE-2026-55872&match=exact; reference:url,https://subdomain.center/?engine=ammonites&keyword=gym-one&match=exact; sid:1084406; rev:1;)

CVE-2026-55872.rules on GitHub

References

Other references

Other databases

Where this comes from

This advisory is generated automatically by VEDAS from: CVE.org record, cve-scores (EPSS and VEDAS), Exploit Observer, vedas-signatures. Text in quotes is reproduced from the source; everything else is a fixed template filled with source fields. Nothing here is written by a language model. Check the vendor advisory before acting, and read how VEDAS and Exploit Observer work, and their limits.