CVE-2026-28809

XML External Entity (XXE) vulnerability in esaml (and its forks) allows an attacker to cause the system to read local files and incorporate their contents into processed SAML documents, and potentially perform SSRF via crafted SAML messages. esaml parses attacker-controlled SAML messages using xmerl_scan:string/2 before signature verification without disabling XML entity expansion. On Erlang/OTP versions before 27, Xmerl allows entities by default, enabling pre-signature XXE attacks. An attacker can cause the host to read local files (e.g., Kubernetes-mounted secrets) into the SAML document. If the attacker is not a trusted SAML SP, signature verification will fail and the document is discarded, but file contents may still be exposed through logs or error messages. This issue affects all versions of esaml, including forks by arekinath, handnot2, and dropbox. Users running on Erlang/OTP 27 or later are not affected due to Xmerl defaulting to entities disabled.

• Arekinath Esaml

  APP
  Arekinath
  ≤ 1.1

• Dropbox Esaml

  APP
  Dropbox
  all versions

• Handnot2 Esaml

  APP
  Handnot2
  ≤ 4.2.0

• Jump App Esaml

  APP
  Jump-App
  ≤ 4.6.0