CVE-2026-77581: BentoPDF: SSRF in cors-proxy-worker.js via DNS-based hostname allowlist bypass

What it is

BentoPDF is a client-side PDF toolkit that is self hostable. In 2.8.6 and earlier, the certificate and timestamp CORS proxy in cloudflare/cors-proxy-worker.js uses isPrivateOrReservedHost() to validate a supplied hostname separately from the DNS resolution used by fetch(targetUrl), allowing an attacker-controlled hostname to resolve to an internal or reserved destination after validation. A certificate-like path can satisfy ALLOWED_PATH_PATTERNS, and direct clients can forge the browser-oriented Origin header. Deployments without PROXY_SECRET skip the optional signature check, while the signature is an anti-abuse measure rather than a destination-security boundary. The proxy has a 10 MB response limit and can relay response bodies from reachable destinations. The advisory identifies both the official Worker deployment and self-hosted instances as impacted where the Worker execution environment can reach internal or reserved destinations. This vulnerability is fixed in 2.8.7.

Description quoted from the CVE record (assigned by GitHub_M, published 2026-09-24).

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 low, availability low. CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L

CISA assessment (SSVC): CISA assesses that a public proof of concept exists. Automatable: yes. Technical impact: partial.

Public exploit evidence (Exploit Observer)

Exploit Observer found 5 code repositories naming this CVE.

Code repositories that name a CVE are often scanners, copies or fakes, and some are malware. Read the code before running anything.

See all 7 references on Exploit Observer

Live scores

EPSS

0.003
low predicted chance of attack

VEDAS

0.988
strong exploit evidence

On CISA KEV

Not listed

Detection rule

Nuclei · Suricata

Who is affected

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)

BentoPDF CORS Proxy - Server-Side Request Forgery

BentoPDF before 2.8.7 ships a certificate/timestamp CORS proxy worker that validates the supplied hostname separately from the DNS resolution used by fetch(targetUrl), and skips the optional signature check when PROXY_SECRET is unset. A remote attacker can supply a url query parameter so the proxy fetches an internal or reserved destination (SSRF).

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

The template sends 1 request (GET /?url=http://{{interactsh-url}}/ca.crt); it confirms through an out-of-band callback (interactsh), so the scanner must be able to receive it; it decides using 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:

nuclei -u https://your-host -t CVE-2026-77581.yaml

id: CVE-2026-77581

info:
  name: "BentoPDF CORS Proxy - Server-Side Request Forgery"
  author: vedas-arpsyndicate
  severity: high
  description: |
    BentoPDF before 2.8.7 ships a certificate/timestamp CORS proxy worker that validates the
    supplied hostname separately from the DNS resolution used by fetch(targetUrl), and skips the
    optional signature check when PROXY_SECRET is unset. A remote attacker can supply a url query
    parameter so the proxy fetches an internal or reserved destination (SSRF).
  reference:
    - https://www.exploit.observer/?keyword=CVE-2026-77581&match=exact
    - https://subdomain.center/?engine=ammonites&keyword=bentopdf&match=exact
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L
    cvss-score: 8.6
    cve-id: CVE-2026-77581
    cwe-id: CWE-918
  metadata:
    verified: false
    max-request: 1
  tags: cve,cve2026,bentopdf,ssrf,oast,proxy,vuln
http:
  - raw:
      - |
        GET /?url=http://{{interactsh-url}}/ca.crt HTTP/1.1
        Host: {{Hostname}}
        Origin: https://www.bentopdf.com

    matchers-condition: and
    matchers:
      - type: word
        part: interactsh_protocol
        words:
          - "http"

CVE-2026-77581.yaml on GitHub

Suricata rules (network detection)

1 rule that alert on traffic matching this exploit: VEDAS CVE-2026-77581 BentoPDF CORS Proxy - Server-Side Request Forgery. Add them to your Suricata rule set and reload.

alert http $EXTERNAL_NET any -> $HOME_NET any (msg:"VEDAS CVE-2026-77581 BentoPDF CORS Proxy - Server-Side Request Forgery"; flow:established,to_server; http.method; content:"GET"; http.uri; content:"url="; nocase; content:"://"; http.header; content:"bentopdf.com"; nocase; fast_pattern; classtype:web-application-attack; reference:cve,CVE-2026-77581; reference:url,https://www.exploit.observer/?keyword=CVE-2026-77581&match=exact; reference:url,https://subdomain.center/?engine=ammonites&keyword=bentopdf&match=exact; sid:1071603; rev:1;)

CVE-2026-77581.rules on GitHub

References

Other references

• https://github.com/alam00000/bentopdf/security/advisories/GHSA-5xjf-rr5x-pcfj (x_refsource_CONFIRM)
• https://github.com/alam00000/bentopdf/commit/45496fcd2ed6e02dcdde0d3839cc5024c091760c (x_refsource_MISC)
• https://github.com/alam00000/bentopdf/commit/58cd1a8893bfe06e4a59a72adc2e7db00a8b9266 (x_refsource_MISC)
• https://github.com/alam00000/bentopdf/releases/tag/v2.8.7 (x_refsource_MISC)

Other databases

• CVE record (cve.org)
• NVD
• Exploit Observer

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.