EEF-CVE-2026-28809 CVE-2026-28809 GHSA-4g2h-vm7x-747c
XXE in esaml SAML library allows local file read and potential SSRF
- Severity
- 0.0 / 10
- Medium · CVSS 4.0
- Exploit chance (EPSS)
- 0.29%
- Chance of exploitation in the next 30 days. Higher than 21.16% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-611 Improper Restriction of XML External Entity Reference
- Fix
- None yet
- No fixed version published
Description
Summary
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.
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.
Affected versions
Hex
How to fix
No fixed version has been published yet. Until one is, remove or replace the package, or turn off or isolate the affected feature. This page updates when a fix ships.
Severity breakdown
CVSS 4.0 0.0
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
- Attack vector
- Network
- Attack complexity
- Low
- Attack requirements
- Present
- Privileges required
- None
- User interaction
- None
- Confidentiality (vulnerable system)
- Low
- Integrity (vulnerable system)
- None
- Availability (vulnerable system)
- None
- Confidentiality (subsequent systems)
- None
- Integrity (subsequent systems)
- None
- Availability (subsequent systems)
- None
CVSS 3.1 5.3
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- None
- Availability
- None
Weakness
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 to prevent it
- Implementation, System Configuration: Many XML parsers and validators can be configured to disable external entity expansion.
References
Advisories
Fixes and patches
Packages
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| EEF-CVE-2026-93471 Unbounded SAML message decompression in esaml allows memory exhaustion | Not rated yet | Also affects esaml |
| EEF-CVE-2026-86696 Unbounded atom creation from unsigned LogoutResponse status codes in esaml allows atom table exhaustion | Not rated yet | Also affects esaml |
| EEF-CVE-2026-105270 Unbounded atom creation while parsing SAML messages in esaml allows atom table exhaustion | Not rated yet | Also affects esaml |
| GHSA-3x94-m842-937c PhpSpreadsheet: XmlScanner Bypass via ISO-2022 Escape Sequences Allows XXE and Denial of Service | High | Same weakness, CWE-611 |
| GHSA-rxj4-h86g-25gc PhpSpreadsheet: XmlScanner Bypass via Double-Encoded unentity() TOCTOU Allows XXE and Denial of Service | High | Same weakness, CWE-611 |
| GHSA-8678-w3jw-xfc2 Nokogiri: XML::Schema on JRuby allows network requests when NONET is set, bypassing CVE-2020-26247 | Low | Same weakness, CWE-611 |
| GHSA-x4r9-gmw3-hxww GeoServer has a Server-Side Request Forgery (SSRF) Vulnerability in its XML Entity Resolution | High | Same weakness, CWE-611 |
| GHSA-x6g4-fwcc-jj8w Symfony has XXE (Local File Disclosure) in DomCrawler::addXmlContent() via validateOnParse = true | High | Same weakness, CWE-611 |
Credits: Bryan Lynch, Jonatan Männchen / EEF
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