CVE-2026-28809 · published 2026-03-23 · updated 2026-07-24

XXE in esaml SAML library allows local file read and potential SSRF

MEDIUM 6.3 CWE-611 · Improper Restriction of XML External Entity Reference
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Am I affected?

This record states its affected versions in a form that can't be compared automatically.

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.

Weaknesses & attack patterns

Weakness

CWE-611 · Improper Restriction of XML External Entity Reference in catalog → MITRE ↗

Attack patterns

CAPEC-201 · Serialized Data External Linking MITRE ↗

Affected — Hex / esaml Hex.pm ↗

All versions affected.

default status affected
cpe cpe:2.3:a:dropbox:esaml:*:*:*:*:*:*:*:*, cpe:2.3:a:arekinath:esaml:*:*:*:*:*:*:*:*, cpe:2.3:a:handnot2:esaml:*:*:*:*:*:*:*:*

Affected — GitHub / arekinath/esaml Repository ↗

All versions affected.

default status affected
cpe cpe:2.3:a:arekinath:esaml:*:*:*:*:*:*:*:*

Affected — GitHub / handnot2/esaml Repository ↗

All versions affected.

default status affected
cpe cpe:2.3:a:handnot2:esaml:*:*:*:*:*:*:*:*

Affected — GitHub / dropbox/esaml Repository ↗

All versions affected.

default status affected
cpe cpe:2.3:a:dropbox:esaml:*:*:*:*:*:*:*:*

Affected — GitHub / jump-app/esaml Repository ↗

≥ deeb843 < bab85ef affected
bab85ef not affected
every other version: affected
default status affected
cpe cpe:2.3:a:jump-app:esaml:*:*:*:*:*:*:*:*

Workarounds

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.

Configurations

The application must use esaml to process SAML messages and run on Erlang/OTP versions before 27. Starting with OTP 27, xmerl_scan disables entity expansion by default, which mitigates this vulnerability.

References

github.com/Jump-App/esaml · bab85ef ↗ patch
osv.dev · EEF-CVE-2026-28809 ↗ related

Credits

Bryan Lynch Finder
Jonatan Männchen / EEF Analyst

CVSS breakdown

MEDIUM 6.3 open in calculator →
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
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