Vulnerability · Published Oct 22, 2026 · Assigned by EEF
CVE-2026-93471Unbounded SAML message decompression in esaml allows memory exhaustion
High 8.7
In plain English
A high-severity security flaw in esaml from arekinath. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.7% (higher than 52% of all known vulnerabilities).
Official 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.
Affected products (as reported)
Weakness: CWE-409 · Vector: 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
References
- EEF CNA record for CVE-2026-93471 related, third-party-advisory
- OSV record EEF-CVE-2026-93471 related
- Introducing commit deeb843 in handnot2/esaml related
- Introducing commit deeb843 in arekinath/esaml related
- Introducing commit deeb843 in dropbox/esaml related, broken-link