CVE-2026-8670Network attack vector

Session hijacking via unexpired Metrics WebServer IDs

Published May 22, 2026 · Updated May 22, 2026

Insufficient session expiration in Avantra before 25.3.1 allows remote attackers to replay Metrics WebServer session IDs. The Metrics WebServer continues accepting a session ID after its originating session should expire, permitting the identifier to be reused. A valid session ID and user interaction are required; replay grants the session holder's access to server metrics and health data.

CVSS severity9.6
Critical
EPSS probability0.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Insufficient session expiration in Avantra before 25.3.1 allows remote attackers to replay Metrics WebServer session IDs. The Metrics WebServer continues accepting a session ID after its originating session should expire, permitting the identifier to be reused. A valid session ID and user interaction are required; replay grants the session holder's access to server metrics and health data.

The record

CVE
CVE-2026-8670
Published
May 22, 2026
Updated
May 22, 2026
Vendor
Syslink Software AG
Product
Avantra
Classifications
CWE-613, CAPEC-60, T1550.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 22, 2026CVE publishedPublication date reported by the CVE source.
  2. May 22, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <25.3.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Syslink Software AG · Avantraversion=0 <25.3.1

Published CVSS scores

9.6Switzerland Government Common Vulnerability ProgramCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-613Insufficient Session Expiration
CAPEC-60Reusing Session IDs (aka Session Replay)
T1550.004Use Alternate Authentication Material: Web Session Cookie

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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