CVE-2026-93471
Unbounded SAML message decompression in esaml allows memory exhaustion
- State
- Published
- Severity
- 8.7 High
- Published
- Oct 22, 2026
- Updated
- Oct 30, 2026
- Reserved
- Oct 6, 2026
Description
Improper Handling of Highly Compressed Data (Data Amplification) in esaml_binding in dropbox esaml allows an unauthenticated attacker to exhaust server memory and crash the Erlang VM via a crafted compressed SAMLResponse.
esaml_binding:decode_response/2 base64-decodes the attacker-supplied SAMLResponse, inflates it with zlib:unzip/1 with no bound on the output, then converts the result to a charlist with binary_to_list/1 before parsing. This runs on the SAML consume (ACS) and single-logout endpoints, which accept unauthenticated requests by design, and it runs before any signature check. A small deflate stream reaches a compression ratio near 1000 to 1, so a request body of tens of kilobytes inflates to hundreds of megabytes and then to several gigabytes of list heap, so a few requests exhaust memory and take the node down.
This issue affects esaml: from 0.1.0 onward.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 8.7 High | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N | EEF |
Weaknesses
- CWE-409 Improper Handling of Highly Compressed Data (Data Amplification)
Affected Products
| Product | Versions |
|---|---|
esamlhandnot2 |
|
esamlarekinath |
|
esamldropbox |
|
esamldropbox |
|
References
- EEF CNA record for CVE-2026-93471relatedthird-party-advisory
- OSV record EEF-CVE-2026-93471related
- Introducing commit deeb843 in handnot2/esamlrelated
- Introducing commit deeb843 in arekinath/esamlrelated
- Introducing commit deeb843 in dropbox/esamlrelatedbroken-link
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