CVE-2026-28809: Esaml Esaml XXE Vulnerability Allows Local Vulnerability

MODERATE
Advisory Identifier: GHSA-4g2h-vm7x-747c
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CWE-611
Published
Advisory Summary

CVE-2026-28809 is a MODERATE esaml xxe vulnerability allows local vulnerability (CWE-611: Improper Restriction of XML External Entity Reference) affecting Esaml libraries in the Hex ecosystem. The issue involves esaml xxe vulnerability allows local file disclosure and ssrf via crafted saml messages. Remediation is available in the latest vendor maintenance releases.

CVE-2026-28809 at a Glance

CVE Identifier CVE-2026-28809
GHSA Identifier GHSA-4g2h-vm7x-747c
Severity MODERATE
CVSS v3.1 Base Score N/A
CWE Classification CWE-611: Improper Restriction of XML External Entity Reference
Affected Product Esaml
Package Ecosystem Hex
Published Date
Last Updated

How to Fix CVE-2026-28809

To remediate this vulnerability, upgrade all affected Esaml dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

esaml fixed: Latest secure release 
Upgrade esaml to Latest secure release
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for esaml

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-28809, inspect your project dependencies for Esaml:

inspect dependencies for esaml

Analyze the terminal output to locate any version of Esaml in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than the patched release), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-611: Improper Restriction of XML External Entity Reference, where the product processes an xml document that can contain xml entities with uris that resolve to documents outside of the intended sphere of control, causing the product to embed incorrect documents into its output. In Esaml, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

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.

CVE-2026-28809 Affected Esaml Versions

1 component(s)
Product / Package Ecosystem Affected Versions Fixed Version
esaml
 Hex
≤ 4.6.0

References

NVD — CVE-2026-28809 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-28809
Security Fix Commit FIX COMMIT
https://github.com/Jump-App/esaml/commit/bab85efde7c136911402a881ca55173759467a26
cna.erlef.org/cves/cve-2026-28809... WEB
https://cna.erlef.org/cves/CVE-2026-28809.html
Esaml Source Repository REPOSITORY
https://github.com/arekinath/esaml
osv.dev/vulnerability/eef-c... WEB
https://osv.dev/vulnerability/EEF-CVE-2026-28809

Frequently Asked Questions

What is CVE-2026-28809?
CVE-2026-28809 is a security vulnerability in Esaml involving esaml XXE vulnerability allows local file disclosure and SSRF via crafted SAML messages under CWE-611: Improper Restriction of XML External Entity Reference.
Which Esaml versions are affected?
Affected versions include releases prior to current release patches across affected packages: esaml.
What version fixes CVE-2026-28809?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
Is esaml affected?
Yes, esaml is affected in releases prior to Latest secure release. Upgrade your dependency to Latest secure release or later.
What CWE is associated with CVE-2026-28809?
CVE-2026-28809 is classified under CWE-611: Improper Restriction of XML External Entity Reference (The product processes an XML document that can contain XML entities with URIs that resolve to documents outside of the intended sphere of control, causing the product to embed incorrect documents into its output.).
How can I check Hex dependencies for CVE-2026-28809?
Run the dependency tree command: 'inspect dependencies for esaml'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-4g2h-vm7x-747c",
  "modified" : "2026-04-06T23:16:15Z",
  "published" : "2026-03-23T12:30:29Z",
  "aliases" : [ "CVE-2026-28809" ],
  "summary" : "esaml XXE vulnerability allows local file disclosure and SSRF via crafted SAML messages",
  "details" : "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.\n\nesaml 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.\n\nThis 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.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "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"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Hex",
      "name" : "esaml"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "4.6.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-28809"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/Jump-App/esaml/commit/bab85efde7c136911402a881ca55173759467a26"
  }, {
    "type" : "WEB",
    "url" : "https://cna.erlef.org/cves/CVE-2026-28809.html"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/arekinath/esaml"
  }, {
    "type" : "WEB",
    "url" : "https://osv.dev/vulnerability/EEF-CVE-2026-28809"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-611" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-25T19:50:48Z",
    "nvd_published_at" : "2026-03-23T11:16:24Z"
  }
}