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CVE Record

CVE-2026-52723: ePA 3.x Integration: VAU Server Authentication Bypass via Circular Certificate Trust

ePA 3.x Integration implements the authorization workflow and writes Medical Information Objects to Germany's electronic patient record. Prior to 1.3.0, ePA 3.x Integration performs VAU server certificate validation in app/vau/VAUProtokoll.py without anchoring the signed_vau_server_pub_keys and AUT_VAU_CertData certificate path to independent trusted material. A network-positioned attacker between the DiGA backend and the ePA system can intercept the VAU handshake, supply attacker-controlled certificate and key material, and satisfy the circular trust relationship. Because TLS certificate verification is also disabled in affected versions, no independent server-authentication layer prevents the attack. The attacker can impersonate the VAU server, control the negotiated session keys, and read or modify all encrypted VAU traffic. This issue is fixed in version 1.3.0.

CriticalCVSS 9.1Not KEV-listedUpdated
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Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

Affected ePA integration deployments may accept an attacker's identity as the trusted VAU server. An attacker positioned on the network path could then read or alter sensitive medical-record traffic. The issue affects versions before 1.3.0 and is especially serious because affected versions also disable TLS certificate verification.

Executive priority

Treat this as an immediate remediation priority wherever the affected integration handles production medical information. The vulnerability can expose or alter protected traffic without credentials or user interaction. Confirm ownership, deploy version 1.3.0 or later promptly, and assess whether affected network paths could previously have been intercepted.

Technical view

Certificate validation in VAUProtokoll.py creates circular trust: attacker-supplied VAU keys and certificate data are validated without an independent trust anchor. With TLS verification also disabled, a network-positioned attacker can impersonate the VAU server, control negotiated session keys, and compromise VAU traffic confidentiality and integrity. Version 1.3.0 fixes the issue.

Likely exposure

Exposure is limited to fbeta-GmbH ePA3-Service-OpenSource deployments running versions earlier than 1.3.0. Exploitation requires a position between the DiGA backend and ePA system, but requires no privileges or user interaction. Environments with interceptable, shared, compromised, or otherwise untrusted network paths face the greatest risk.

Exploitation context

The supplied sources do not establish active exploitation, and the bundle reports that this CVE is not in KEV. The CVSS 9.1 assessment reflects network reachability, low attack complexity, no required privileges or user action, and potentially complete loss of traffic confidentiality and integrity.

Researcher notes

The core weakness is CWE-295 certificate validation failure, specifically circular trust between signed VAU public keys and AUT_VAU_CertData. The absence of separately trusted material removes independent server identity verification. Disabled TLS verification eliminates a possible secondary authentication boundary. The supplied bundle identifies the fixing release and commit but provides no evidence of exploitation in the wild.

Mitigation direction

  • Upgrade every affected deployment to version 1.3.0 or later.
  • Consult the vendor advisory and release notes before deploying the update.
  • Until upgraded, restrict the DiGA-to-ePA network path to trusted, controlled infrastructure.
  • Treat potentially intercepted medical data as sensitive incident-response scope.

Validation and detection

  • Inventory deployments and identify every instance running a version earlier than 1.3.0.
  • Confirm production artifacts match the official 1.3.0 or later release.
  • Verify VAU authentication rejects certificate paths lacking an independent trusted anchor.
  • Confirm TLS certificate verification is enabled after remediation.
  • Review relevant telemetry for unexpected VAU endpoints, certificates, or network-path changes.
Prepared
Confidence
high
Sources
6

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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ATT&CK lookup starting points

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cwe · low confidence lookup

CWE-295: Exact CWE lookup

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description · low confidence lookup

Credential and access behavior lookup

The CVE wording references authentication or credential exposure, so valid-account and credential-access review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

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cve · low confidence lookup

CVE-2026-52723 mapping review

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Vulnerability profileCVE Program record
Severity
Critical
CVSS
9.1 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
3Timeline events
1ADP providers
6Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: yesTechnical Impact: total

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
9.1CVSS 3.1CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N3.95.2GitHub_M

Vulnerability scoring details

Base CVSS 3.1 score

9.1Critical
CVSS 3.1 vector shape for CVE-2026-52723Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
fbeta-GmbHePA3-Service-OpenSource< 1.3.0Listed
Weakness

CWE details

CWE-295

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-295 · source CWE mapping

Improper Certificate Validation

Improper Certificate Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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