CVE-2026-28809
MediumCVSS 5.3Exploitation Probability (EPSS)
Low risk20th percentile - higher than 20% of all known CVEs
Summary
The esaml library (and its forks) has an XXE vulnerability. Before signature verification, esaml parses attacker-controlled SAML messages using xmerl_scan:string/2 without disabling XML entity expansion. On Erlang/OTP before version 27, Xmerl allows entities by default, enabling pre-signature XXE attacks. An attacker can read local files (e.g., Kubernetes secrets) and include their contents in the SAML document.
Risk Assessment
An attacker can read sensitive files from the system, such as Kubernetes secrets, potentially leading to credential leakage and privilege escalation.
Recommendation
Upgrade Erlang/OTP to version 27 or later where XML entities are disabled by default, and apply the esaml patch once available.
Original NVD description (English source)
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.