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CVE-2026-93471— Unbounded SAML message decompression in esaml allows memory exhaustion

Quick assessment

Affected
handnot2 esaml
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Dropbox 的 esaml 库中，esaml_binding 模块在处理高度压缩数据时存在不当处理（即数据放大漏洞），允许未认证的攻击者通过精心构造的压缩 SAMLResponse 耗尽服务器内存，进而导致 Erlang 虚拟机（VM）崩溃。 具体而言， 函数会先对攻击者提供的 SAMLResponse 进行 Base64 解码，随后使用 对其进行解压缩，且未对输出大小设置任何限制；之后，该函数再通过 将解压缩结果转换为字符列表（charlist），最后才进行解析。此处理流程运行于 SAML 消费端（ACS）和

CVSS 8.7 · High

Possible ATT&CK Techniques 1 AI

T1499.003 · Application Exhaustion Flood
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I. Basic Information for CVE-2026-93471

Vulnerability Information
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Vulnerability Title
Unbounded SAML message decompression in esaml allows memory exhaustion
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
对高度压缩数据的处理不恰当(数据放大攻击)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
handnot2 esaml deeb84378d5c82153b470e99d24f77c38afca14a ~ * cpe:2.3:a:handnot2:esaml:*:*:*:*:*:*:*:*
arekinath esaml deeb84378d5c82153b470e99d24f77c38afca14a ~ * cpe:2.3:a:arekinath:esaml:*:*:*:*:*:*:*:*
dropbox esaml 0.1.0 ~ * cpe:2.3:a:dropbox:esaml:*:*:*:*:*:*:*:*
dropbox esaml deeb84378d5c82153b470e99d24f77c38afca14a ~ * cpe:2.3:a:dropbox:esaml:*:*:*:*:*:*:*:*

II. Public POCs for CVE-2026-93471

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III. Intelligence Information for CVE-2026-93471

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Other References for CVE-2026-93471 (5)

IV. Related Vulnerabilities

Same product: esaml
Same vendor: handnot2
Same weakness: CWE-409

V. Comments for CVE-2026-93471

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