VULNpocalypse

CVE-2026-34206: Captcha Protect: Reflected XSS in challenge page via unsanitized destination rendered with text/template

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

Captcha Protect is a Traefik middleware to add an anti-bot challenge to individual IPs in a subnet when traffic spikes are detected from that subnet. Prior to version 1.12.2, a reflected cross-site scripting (XSS) vulnerability exists in github.com/libops/captcha-protect. The challenge page accepted a client-supplied destination value and rendered it into HTML using Go’s text/template. Because text/template does not perform contextual HTML escaping, an attacker could supply a crafted destination value that breaks out of the hidden input attribute and injects arbitrary script into the challenge page. This issue has been patched in version 1.12.2.

Description quoted from the CVE record (assigned by GitHub_M, published 2026-03-31).

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 no privileges and a user must take an action. Impact: confidentiality low, integrity low, availability none. CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

CISA assessment (SSVC): CISA has no evidence of exploitation. Automatable: no. Technical impact: partial.

Public exploit evidence (Exploit Observer)

Also known as: EUVD-2026-17602

VEDAS cluster: VEDAS:CRYSTALVOYAGE

Exploit Observer links 5 pieces of public exploit code or detection modules that name this CVE or one of its aliases.

Exploit code and modules (5)

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
0.002
low predicted chance of attack
VEDAS
0.988
strong exploit evidence
On CISA KEV
Not listed
Detection rule
Nuclei · Suricata

Who is affected

ProductAffectedNot affected
libops captcha-protectversion < 1.12.2Not stated

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

Exploit Observer also maps it to: libops captcha_protect.

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

Nuclei template (active check)

Captcha Protect - Reflected Cross-Site Scripting

Captcha Protect is a Traefik middleware that presents an anti-bot challenge to IPs in a subnet when traffic spikes are detected. Prior to version 1.12.2, the challenge page (GET /challenge) reflected the client-supplied `destination` query parameter into the page’s hidden input using Go’s text/template, which performs no contextual HTML escaping. An unauthenticated attacker can supply a crafted `destination` value that breaks out of the value attribute and injects arbitrary script into the challenge page.

Name and description quoted from the template, written by VEDAS.

The template sends 1 request (GET /challenge?destination=vedasINJ%22%3E%3Csvg%2Fonload%3Dalert%281%29%3E); it decides using status, word matchers. Severity in the template: medium. Marked as not yet verified against a live vulnerable target.

Run it against a host you own or are authorised to test:

bash
nuclei -u https://your-host -t CVE-2026-34206.yaml
Show the template (45 lines)
yaml
id: CVE-2026-34206

info:
  name: "Captcha Protect - Reflected Cross-Site Scripting"
  author: vedas-arpsyndicate
  severity: medium
  description: |
    Captcha Protect is a Traefik middleware that presents an anti-bot challenge to IPs in a
    subnet when traffic spikes are detected. Prior to version 1.12.2, the challenge page
    (GET /challenge) reflected the client-supplied `destination` query parameter into the
    page's hidden input using Go's text/template, which performs no contextual HTML escaping.
    An unauthenticated attacker can supply a crafted `destination` value that breaks out of the
    value attribute and injects arbitrary script into the challenge page.
  reference:
    - https://www.exploit.observer/?keyword=CVE-2026-34206&match=exact
    - https://subdomain.center/?engine=ammonites&keyword=captcha-protect&match=exact
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
    cvss-score: 6.1
    cve-id: CVE-2026-34206
    cwe-id: CWE-79
  metadata:
    verified: false
    max-request: 1
  tags: cve,cve2026,captcha-protect,traefik,xss
http:
  - method: GET
    path:
      - "{{BaseURL}}/challenge?destination=vedasINJ%22%3E%3Csvg%2Fonload%3Dalert%281%29%3E"

    matchers-condition: and
    matchers:
      - type: word
        part: body
        words:
          - 'vedasINJ"><svg/onload=alert(1)>'

      - type: word
        part: header
        words:
          - "text/html"

      - type: status
        status:
          - 200

CVE-2026-34206.yaml on GitHub

Suricata rules (network detection)

1 rule that alert on traffic matching this exploit: VEDAS CVE-2026-34206 Captcha Protect - Reflected XSS via destination Parameter. 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-2026-34206 Captcha Protect - Reflected XSS via destination Parameter"; flow:established,to_server; http.method; content:"GET"; http.uri; content:"/challenge"; nocase; fast_pattern; content:"destination="; nocase; pcre:"/[?&]destination=[^&]*(?:(?:%3c|<)\s*(?:svg|script|img|iframe|body|details)|on(?:load|error|click|mouseover|focus)\s*(?:%3d|=))/i"; classtype:web-application-attack; reference:cve,CVE-2026-34206; reference:url,https://www.exploit.observer/?keyword=CVE-2026-34206&match=exact; reference:url,https://subdomain.center/?engine=ammonites&keyword=captcha-protect&match=exact; sid:1098400; rev:1;)

CVE-2026-34206.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.