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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.

PUBLISHED Reserved 2026-03-03 | Published 2026-03-23 | Updated 2026-05-27 | Assigner EEF




MEDIUM: 6.3CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N

Problem types

CWE-611 Improper Restriction of XML External Entity Reference

Product status

Default status
affected

Default status
affected

Default status
affected

Default status
affected

Default status
affected

Any version before bab85efde7c136911402a881ca55173759467a26
affected

bab85efde7c136911402a881ca55173759467a26 (git)
unaffected

Credits

Bryan Lynch finder

Jonatan Männchen / EEF analyst

References

cna.erlef.org/cves/CVE-2026-28809.html third-party-advisory related

osv.dev/vulnerability/EEF-CVE-2026-28809 related

github.com/...ommit/bab85efde7c136911402a881ca55173759467a26 patch

cve.org (CVE-2026-28809)

nvd.nist.gov (CVE-2026-28809)

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