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.

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Advisories

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Fixes

Solution

No solution given by the vendor.


Workaround

Upgrade to Erlang/OTP 27 or later. Starting with OTP 27, xmerl_scan disables entity expansion by default, which mitigates this vulnerability without changes to esaml.

History

Mon, 23 Mar 2026 10:45:00 +0000

Type Values Removed Values Added
Description 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.
Title XXE in esaml SAML library allows local file read and potential SSRF
First Time appeared Arekinath
Arekinath esaml
Dropbox
Dropbox esaml
Handnot2
Handnot2 esaml
Weaknesses CWE-611
CPEs cpe:2.3:a:arekinath:esaml:*:*:*:*:*:*:*:*
cpe:2.3:a:dropbox:esaml:*:*:*:*:*:*:*:*
cpe:2.3:a:handnot2:esaml:*:*:*:*:*:*:*:*
Vendors & Products Arekinath
Arekinath esaml
Dropbox
Dropbox esaml
Handnot2
Handnot2 esaml
References
Metrics cvssV4_0

{'score': 6.3, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: EEF

Published:

Updated: 2026-03-23T15:52:46.187Z

Reserved: 2026-03-03T14:40:00.590Z

Link: CVE-2026-28809

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-03-23T11:16:24.343

Modified: 2026-03-23T14:31:37.267

Link: CVE-2026-28809

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses