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Full vulnerability report · 2026
CVE-2025-3756High confidence

Denial of Service Vulnerabilities in System 800xA, Symphony® Plus IEC 61850

ABB · AC800M (System 800xA)

7.1HighCVSS 4.0
Recommended action
Within 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

1 current
7PAA020125 · CSAF 2.0 · revision 1 · finalABB Product Security Incident Response Team (PSIRT)Denial of Service Vulnerabilities in System 800xA, Symphony® Plus IEC 61850 communication stack
16 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • ABB Firmware <=6.0.0303.0 (AC800M version 6.0.0-x) installed on ABB AC800M Product line (System 800xA) CI868 for IEC 61850 communication
  • ABB Firmware <=1.0031.0 (AC800M version 6.1.0-x) installed on ABB AC800M Product line (System 800xA) CI868 for IEC 61850 communication
  • ABB Firmware <=6.1.1004.0 AC800M version 6.1.1-0 and 6.1.1-1) installed on ABB AC800M Product line (System 800xA) CI868 for IEC 61850 communication
  • ABB Firmware <=6.1.1202.0 (AC800M version 6.1.1-2) installed on ABB AC800M Product line (System 800xA) CI868 for IEC 61850 communication
  • ABB Firmware <=6.2.0006.0 (AC800M version 6.2.0-0) installed on ABB AC800M Product line (System 800xA) CI868 for IEC 61850 communication
  • ABB Firmware A_0 installed on ABB Symphony Plus SD Series CI850 for IEC 61850 communication
  • ABB Firmware A_1 installed on ABB Symphony Plus SD Series CI850 for IEC 61850 communication
  • ABB Firmware A_2.003 installed on ABB Symphony Plus SD Series CI850 for IEC 61850 communication
  • ABB Firmware A_3.005 installed on ABB Symphony Plus SD Series CI850 for IEC 61850 communication
  • ABB Firmware A_4.001 installed on ABB Symphony Plus SD Series CI850 for IEC 61850 communication
  • ABB Firmware B_0.005 installed on ABB Symphony Plus SD Series CI850 for IEC 61850 communication
  • ABB Firmware >=3.10|<=3.52 installed on ABB Symphony Plus MR (Melody Rack) PM 877 for IEC 61850 communication
Summary
A vulnerability exists in the command handling of the IEC 61850 communication stack included in the product revisions listed above. An attacker with access to IEC 61850 networks could exploit the vulnerability by using a specially crafted 61850 packet, forcing the communication interfaces of the PM 877, CI850 and CI868 modules into fault mode or causing unavailability of the S+ Operations 61850 connectivity, resulting in a denial-of-service situation. The System 800xA IEC61850 Connect is not affected. Note: This vulnerability does not impact on the overall availability and functionality of the S+ Operations node, only the 61850 communication function.
Remediation
ABB advises all customers to review their installations to determine if they are using an impacted product as listed above, no further analysis or tools are needed to make this determination. The recommended immediate actions per product are listed below: - CI868 (for AC 800M) Devices with firmware versions reported in Affected products are vulnerable. All the vulnerabilities will be corrected in 6.1.1 and 7.0 tracks for 800xA. AC 800M 6.1.1-3 is planned for Q2 2027, AC 800M 7.0 has been released in December 2025. - CI850 (for Symphony Plus SD Series) Devices with firmware versions reported in Affected products are vulnerable. All the vulnerabilities will be corrected in version C_0 or later (planned Q2 2026). - PM 877 (Symphony Plus MR) Devices with firmware versions reported in Affected products are vulnerable. All the vulnerabilities will be corrected with firmware version 3.53 or later (planned Q1 2026). - S+ Operations Versions reported in Affected products are vulnerable. All the vulnerabilities will be corrected in version 3.4 or later (released in January 2026). ABB recommends customers apply updates, as they become available, at their earliest convenience. It is also advisable to review the Mitigating Factors, Workarounds and General security recommendations sections for additional actions which may help reduce overall risk.
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Select the national-authority views to include. The exact source language is shown on each matched advisory. Your choice is remembered on this device and encoded in the shareable URL.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2025-209425

No EUVD known-exploited evidence

ENISA has published the identifier mapping but no EUVD description has been stored yet.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
Not supplied in the stored EUVD record
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
01

What, why and how

A vulnerability exists in the command handling of the IEC 61850 communication stack included in the product revisions listed as affected in this CVE. An attacker with access to IEC 61850 networks could exploit the vulnera bility by using a specially crafted 61850 packet, forcing the communication interfaces of the PM 877, CI850 and CI868 modules into fault mode or causing unavailability of the S+ Operations 61850 connectivity, resulting in a denial-of-service situation.  The System 800xA IEC61850 Connect is not affected. Note: This vulnerability does not impact on the overall availability and functionality of the S+ Operations node, only the 61850 communication function.     This issue affects AC800M (System 800xA): from 6.0.0x through 6.0.0303.0, from 6.1.0x through 6.1.0031.0, from 6.1.1x through 6.1.1004.0, from 6.1.1x through 6.1.1202.0, from 6.2.0x through 6.2.0006.0; Symphony Plus SD Series: A_0, A_1, A_2.003, A_3.005, A_4.001, B_0.005; Symphony Plus MR (Melody Rack): from 3.10 through 3.52; S+ Operations: 2.1, 2.2, 2.3, 3.3.

What

A vulnerability exists in the command handling of the IEC 61850 communication stack included in the product revisions listed as affected in this CVE. An attacker with access to IEC 61850 networks could exploit the vulnera bility by using a specially crafted 61850 packet, forcing the communication interfaces of the PM 877, CI850 and CI868 modules into fault mode or causing unavailability of the S+ Operations 61850 connectivity, resulting in a denial-of-service situation.  The System 800xA IEC61850 Connect is not affected. Note: This vulnerability does not impact on the overall availability and functionality of the S+ Operations node, only the 61850 communication function.     This issue affects AC800M (System 800xA): from 6.0.0x through 6.0.0303.0, from 6.1.0x through 6.1.0031.0, from 6.1.1x through 6.1.1004.0, from 6.1.1x through 6.1.1202.0, from 6.2.0x through 6.2.0006.0; Symphony Plus SD Series: A_0, A_1, A_2.003, A_3.005, A_4.001, B_0.005; Symphony Plus MR (Melody Rack): from 3.10 through 3.52; S+ Operations: 2.1, 2.2, 2.3, 3.3.

Why

The product receives input that is expected to specify a quantity (such as size or length), but it does not validate or incorrectly validates that the quantity has the required properties.

How

An attacker operating through an adjacent network may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

What

A vulnerability exists in the command handling of the IEC 61850 communication stack included in the product revisions listed as affected in this CVE. An attacker with access to IEC 61850 networks could exploit the vulnera bility by using a specially crafted 61850 packet, forcing the communication interfaces of the PM 877, CI850 and CI868 modules into fault mode or causing unavailability of the S+ Operations 61850 connectivity, resulting in a denial-of-service situation.  The System 800xA IEC61850 Connect is not affected. Note: This vulnerability does not impact on the overall availability and functionality of the S+ Operations node, only the 61850 communication function.     This issue affects AC800M (System 800xA): from 6.0.0x through 6.0.0303.0, from 6.1.0x through 6.1.0031.0, from 6.1.1x through 6.1.1004.0, from 6.1.1x through 6.1.1202.0, from 6.2.0x through 6.2.0006.0; Symphony Plus SD Series: A_0, A_1, A_2.003, A_3.005, A_4.001, B_0.005; Symphony Plus MR (Melody Rack): from 3.10 through 3.52; S+ Operations: 2.1, 2.2, 2.3, 3.3.

Why

The product receives input that is expected to specify a quantity (such as size or length), but it does not validate or incorrectly validates that the quantity has the required properties.

How

An attacker operating through an adjacent network may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
an adjacent network → Improper Validation of Specified Quantity in Input → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Adjacent
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Not a CVSS 4.0 base metric
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-1284 ↗

CWE-1284: Improper Validation of Specified Quantity in Input. The product receives input that is expected to specify a quantity (such as size or length), but it does not validate or incorrectly validates that the quantity has the required properties.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Common Vulnerability Scoring System 4.0: the compact vector below is decoded into plain language.

AVAdjacentAttack vector: The attacker must be on an adjacent or logically close network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.ATNoneAttack requirements: No additional deployment or execution condition is required.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.VCNoneVulnerable-system confidentiality: No direct loss is represented by this metric.VINoneVulnerable-system integrity: No direct loss is represented by this metric.VAHighVulnerable-system availability: A successful attack can cause a major loss.SCNoneSubsequent-system confidentiality: No direct loss is represented by this metric.SINoneSubsequent-system integrity: No direct loss is represented by this metric.SANoneSubsequent-system availability: No direct loss is represented by this metric.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
UnauthenticatedCWE-1284
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

BSI · German · WID-SEC-W-2026-1086ABB 800xA CI868 (für AC 800M) und PM877 (Symphony Plus MR): Schwachstelle ermöglicht Denial of Service

Ein Angreifer aus einem angrenzenden Netzwerk kann eine Schwachstelle in ABB 800xA und ABB Symphony Melody ausnutzen, um einen Denial of Service Angriff durchzuführen.

Official advisory
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Patch available
Affected
ABB Firmware <=6.0.0303.0 (AC800M version 6.0.0-x) installed on ABB AC800M Product line (System 800xA) CI868 for IEC 61850 communication; ABB Firmware <=1.0031.0 (AC800M version 6.1.0-x) installed on ABB AC800M Product line (System 800xA) CI868 for IEC 61850 communication; ABB Firmware <=6.1.1004.0 AC800M version 6.1.1-0 and 6.1.1-1) installed on ABB AC800M Product line (System 800xA) CI868 for IEC 61850 communication; ABB Firmware <=6.1.1202.0 (AC800M version 6.1.1-2) installed on ABB AC800M Product line (System 800xA) CI868 for IEC 61850 communication; ABB Firmware <=6.2.0006.0 (AC800M version 6.2.0-0) installed on ABB AC800M Product line (System 800xA) CI868 for IEC 61850 communication; ABB Firmware A_0 installed on ABB Symphony Plus SD Series CI850 for IEC 61850 communication; ABB Firmware A_1 installed on ABB Symphony Plus SD Series CI850 for IEC 61850 communication; ABB Firmware A_2.003 installed on ABB Symphony Plus SD Series CI850 for IEC 61850 communication; ABB Firmware A_3.005 installed on ABB Symphony Plus SD Series CI850 for IEC 61850 communication; ABB Firmware A_4.001 installed on ABB Symphony Plus SD Series CI850 for IEC 61850 communication; ABB Firmware B_0.005 installed on ABB Symphony Plus SD Series CI850 for IEC 61850 communication; ABB Firmware >=3.10|<=3.52 installed on ABB Symphony Plus MR (Melody Rack) PM 877 for IEC 61850 communication; ABB Firmware 3.3 and related service packs installed on ABB S+ Operations using IEC 61850 connectivity; ABB Firmware 2.3 installed on ABB S+ Operations using IEC 61850 connectivity; ABB Firmware 2.2 and related service packs installed on ABB S+ Operations using IEC 61850 connectivity; ABB Firmware 2.1 and related service packs installed on ABB S+ Operations using IEC 61850 connectivity
Fixed
ABB Firmware 6.1.1-3 planned for Q2 2027 installed on ABB AC800M Product line (System 800xA) CI868 for IEC 61850 communication; ABB Firmware 7.0 released in Dec 2025 installed on ABB AC800M Product line (System 800xA) CI868 for IEC 61850 communication; ABB Firmware C_0 planned Q2 2026 installed on ABB Symphony Plus SD Series CI850 for IEC 61850 communication; ABB Firmware 3.53 (planned Q1 2026) installed on ABB Symphony Plus MR (Melody Rack) PM 877 for IEC 61850 communication; ABB Firmware 3.4 (released in January 2026) installed on ABB S+ Operations using IEC 61850 connectivity
Action
ABB advises all customers to review their installations to determine if they are using an impacted product as listed above, no further analysis or tools are needed to make this determination. The recommended immediate actions per product are listed below: - CI868 (for AC 800M) Devices with firmware versions reported in Affected products are vulnerable. All the vulnerabilities will be corrected in 6.1.1 and 7.0 tracks for 800xA. AC 800M 6.1.1-3 is planned for Q2 2027, AC 800M 7.0 has been released in December 2025. - CI850 (for Symphony Plus SD Series) Devices with firmware versions reported in Affected products are vulnerable. All the vulnerabilities will be corrected in version C_0 or later (planned Q2 2026). - PM 877 (Symphony Plus MR) Devices with firmware versions reported in Affected products are vulnerable. All the vulnerabilities will be corrected with firmware version 3.53 or later (planned Q1 2026). - S+ Operations Versions reported in Affected products are vulnerable. All the vulnerabilities will be corrected in version 3.4 or later (released in January 2026). ABB recommends customers apply updates, as they become available, at their earliest convenience. It is also advisable to review the Mitigating Factors, Workarounds and General security recommendations sections for additional actions which may help reduce overall risk.
Workaround
No verified workaround is recorded. Limit untrusted access and use least privilege until authoritative guidance is available.
04

Evidence and provenance

Published 13 Apr 2026 · Last source change 13 Apr 2026, 18:03 UTC · CWE-1284 · Improper Validation of Specified Quantity in Input

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2025-209425
Product sourceVendor CSAF · ABB Product Security Incident Response Team (PSIRT)
Remediation sourceVendor CSAF · ABB Product Security Incident Response Team (PSIRT)
CWE sourceCNA
NVD statusNVD not scheduled

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates →
  1. Vendor guidanceAuthoritative vendor guidance changed from authoritative remediation link to authoritative remediation link.
    Before
    authoritative remediation link
    After
    authoritative remediation link
    ABB Product Security Incident Response Team (PSIRT) ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
ENISA EUVD · EUVD-2025-209425↗CVE authority or vendor reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2025-3756 · cve.blacktree.nl