CVE Intelligence
High

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

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.

Published Oct 22, 2026 · Updated Oct 22, 2026 · Sources: CVE Program (cve.org) e CISA ADP, NIST National Vulnerability Database · CNA: EEF

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.
How the score was calculated
  • EPSS 0.4% (30-day exploitation probability)+6
  • Technical severity (high)+6

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Not confirmed
Not in CISA KEV — an absence of record, not proof it is unexploited.
EPSS FIRST
0.44%
ahead of 37% of scored CVEs · Oct 22, 2026
Affects
Arekinath
Esaml
CVSS base
8.7
High · 2 source(s)

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Arekinath Esaml, Dropbox Esaml, Handnot2 Esaml).
  2. The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
  3. No fix documented in the sources: reduce exposure and monitor the vendor advisory.
  4. Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Arekinath Esaml ≥ deeb84378d5c82153b470e99d24f77c38afca14a Vulnerable CVE Program (cve.org) e CISA ADP
Dropbox Esaml ≥ 0.1.0≥ deeb84378d5c82153b470e99d24f77c38afca14a Vulnerable CVE Program (cve.org) e CISA ADP
Handnot2 Esaml ≥ deeb84378d5c82153b470e99d24f77c38afca14a Vulnerable CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Network
Attack complexity
Low
Attack requirements
None
Privileges required
None
User interaction
None
Scope
X
Confidentiality (vulnerable system)
None
Integrity (vulnerable system)
None
Availability (vulnerable system)
High
Confidentiality (subsequent)
None
Integrity (subsequent)
None
Availability (subsequent)
None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
8.7 CVSS 4.0 High — — 6b3ad84c-e1a6-4bf7-a703-f496b71e49db via NIST National Vulnerability Database
8.7 CVSS 4.0 High — — EEF via CVE Program (cve.org) e CISA ADP
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X (score shown at the top: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-409

Other CVEs with this weakness →

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
web/proxy/WAF logsnetwork IDS/IPS

Timeline

What happened to this CVE, newest first.

  • 2026
  • Source status changed · Received → Deferred
    Oct 22, 2026 · NIST National Vulnerability Database
  • Source status changed · Published → Received
    Oct 22, 2026 · NIST National Vulnerability Database
  • CVE published
    Oct 22, 2026 · EEF
  • Record published
    Oct 22, 2026
  • CVSS changed · 8.7
    Oct 22, 2026 · CVE Program (cve.org) e CISA ADP
  • Source status changed · → Published
    Oct 22, 2026 · CVE Program (cve.org) e CISA ADP
  • Record created in this database
    Oct 22, 2026 · CVE Program (cve.org) e CISA ADP

Source activity

Repeated readings are counted rather than listed.

  • 1× Official description updated · Oct 22, 2026 – Oct 22, 2026

References

5 on the record

Elsewhere on this site

Arekinath
every CVE for this vendor
CWE-409
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-86696 Unbounded atom creation from unsigned LogoutResponse status codes in esaml allows atom table exhaustion 1d
  • CVE-2026-105270 Unbounded atom creation while parsing SAML messages in esaml allows atom table exhaustion 1d
  • CVE-2026-28809 XXE in esaml SAML library allows local file read and potential SSRF Mar 23, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No fixed version, patch or mitigation documented.
  • No CISA SSVC assessment.
  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-93471 is "Unbounded SAML message decompression in esaml allows memory exhaustion", rated High. It affects Esaml (Arekinath); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 8.7 describes technical severity. EPSS 0.44% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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