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IBM Server Firmware EUVDEUVD-2026-62683

| CVE-2026-18681 MEDIUM
Stack-based Buffer Overflow (CWE-121)
2026-08-19 ibm GHSA-29hj-6ffg-89rh
6.8
CVSS 3.1 · Vendor: ibm
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Obtain FSP administrator credentials
  2. Delivery
    Gain access to out-of-band management network
  3. Exploit
    Initiate FSP firmware update operation
  4. Execution
    Deliver crafted malicious firmware payload
  5. Persist
    Trigger stack-based buffer overflow in update handler
  6. Impact
    Execute arbitrary code on FSP management controller

Vulnerability Assessment

Weakness
CWE
ASVS 5.0
V15 - Secure Coding and Architecture Stack buffer bounds checking
MITRE ATT&CK

1 technique across 1 tactic: Execution

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Exploitation Conditions

Two specific, independent conditions must both be satisfied: (1) the attacker must hold authenticated administrator-level access to the FSP - standard read-only or unprivileged FSP accounts are insufficient, and host OS administrator access does not automatically grant FSP admin rights; and (2) the attacker must have network adjacency to the FSP management interface (AV:A), typically requiring access to the out-of-band management VLAN or BMC network segment, which is normally isolated from production and internet-facing networks. The vulnerability is triggered specifically within the FSP firmware update process, meaning exploitation requires initiating a firmware update operation with a crafted payload. Additionally, the description states exploitation occurs 'under specific conditions,' which may imply further environmental or state prerequisites not fully enumerated in the CVE description - these specific conditions are not defined in available public data. What limits exploitation: the high privilege requirement (PR:H) is the primary barrier; management network isolation (AV:A) provides a secondary architectural barrier; and the 'specific conditions' qualifier suggests exploitation may not be reliably reproducible across all configurations.

Impact

The NVD-assigned CVSS 3.1 score of 6.8 (Medium) accurately captures the constrained exploitability despite maximum impact: the adjacent network vector (AV:A) requires access to the typically air-gapped or VLAN-isolated BMC management network, and PR:H mandates pre-existing FSP administrator credentials - two independent, high-barrier prerequisites. Organizations that enforce strict out-of-band network segmentation and least-privilege FSP account management face substantially lower real-world risk than the C:H/I:H/A:H impact metrics alone suggest. The description's qualifier 'under specific conditions' may indicate additional environmental prerequisites beyond what the AC:L assignment implies, suggesting the official vector may slightly overstate exploitability. No EPSS score was provided in the input data; exploitation probability cannot be quantified. No CISA KEV listing and no POC code have been identified, indicating this is not known to be actively exploited at time of analysis. The primary risk scenario is insider threat or post-compromise lateral movement by an attacker who has already obtained admin-level management network access, not opportunistic internet-based exploitation.

Exploit ScenarioDerived

An attacker who has obtained FSP administrator credentials - through phishing, credential stuffing against the management interface, or insider access - and who can reach the FSP management network initiates a firmware update operation using a specially crafted malicious firmware image. The crafted payload triggers a stack-based buffer overflow in the FSP update processing routine, overwriting a saved return address on the stack and redirecting execution to attacker-controlled shellcode running within the FSP firmware, granting persistent, OS-independent control over server power, sensors, and boot media. No public proof-of-concept code has been identified at time of analysis.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
Patch available 0.3% exploitation probability (EPSS)

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AnalysisAIv1 – Aug 19, 2026

Stack-based buffer overflow in IBM Server Firmware's FSP firmware update process allows an authenticated administrator with adjacent network access to execute arbitrary code on the Flexible Service Processor, fully compromising the server management plane across confidentiality, integrity, and availability. Affected firmware spans four major release trains (FW950 through FW1120) deployed on IBM Power Systems servers. No public exploit code has been identified at time of analysis and this vulnerability does not appear in the CISA KEV catalog, but the complete C:H/I:H/A:H impact profile makes patching a priority for any organization where FSP admin credentials or management network access could be shared or compromised.

RemediationAI

IBM has released a patch addressing this vulnerability; consult the official IBM security advisory at https://www.ibm.com/support/pages/node/7283899 for exact fixed firmware version numbers for each affected train (FW950, FW1060, FW1110, FW1120) - the input data confirms patch availability from vendor but does not specify precise fix version strings, so the advisory must be consulted before deployment. As compensating controls prior to patching: restrict FSP and BMC management network access to dedicated, access-controlled jump hosts and enforce strict ACLs on the out-of-band management VLAN to eliminate adjacency for unauthorized systems (this reduces the attack surface but does not remove the vulnerability); audit and prune FSP administrator account assignments to enforce least privilege, since PR:H is the primary gatekeeping barrier; and enable FSP audit logging where available to detect anomalous firmware update operations. Note that VLAN segmentation alone does not protect against insider threats or scenarios where a jump host is also compromised.

Affected VersionsENISA

Server Firmware FW1110.00 ≤FW1110.30
Server Firmware FW950.00 ≤FW950.H2
Server Firmware FW1060.00 ≤FW1060.80
Server Firmware FW1120.00

Affects your stack

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Technical ContextAI · show details

The Flexible Service Processor (FSP) is an embedded out-of-band management controller in IBM Power Systems servers, functionally analogous to a BMC or iLO, responsible for power management, environmental monitoring, boot control, and firmware updates independent of the host OS. The vulnerability is classified as CWE-121 (Stack-based Buffer Overflow): during the FSP firmware update process, a specially crafted payload can write beyond the bounds of a stack-allocated buffer, overwriting adjacent stack memory including saved return addresses or function pointers, enabling attacker-controlled code execution within the FSP firmware context. The affected CPE is cpe:2.3:a:ibm:server_firmware:*:*:*:*:*:*:*:*, spanning FW950.00-FW950.H2, FW1060.00-FW1060.80, FW1110.00-FW1110.30, and FW1120.00. Because the FSP operates below the host OS and hypervisor, code execution here can survive OS reinstallation and is difficult to detect through conventional host-based security tools.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (ibm) PRIMARY 6.8 MEDIUM
AV:A/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
vuln.today AI 6.4 MEDIUM

Adjacent vector confirmed by FSP management network requirement; PR:H for mandatory FSP admin authentication; AC:H reflects the 'specific conditions' qualifier in description, diverging from the official AC:L assignment.

3.1 AV:A/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
4.0 AV:A/AC:H/AT:P/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Primary rating from Vendor (ibm).

CVSS VectorVendor: ibm

Attack Vector
Adjacent
Attack Complexity
Low
Privileges Required
High
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

DescriptionCVE.org

IBM Server Firmware FW1120.00, FW1110.00 through FW1110.30, FW1060.00 through FW1060.80, and FW950.00 through FW950.H2 is affected by a vulnerability in the FSP firmware update process. An attacker with authenticated administrator-level access to the FSP can, under specific conditions, execute arbitrary code, resulting in a confidentiality, integrity, and availability impact.

Threat Intelligence Overview

EPSS Score
0.3%
Top 73% exploitable
Prevalence
Low
IBM Power Systems enterprise servers, niche deployment outside large enterprise and government
Data Quality
5 sources
Confidence: Medium

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity MEDIUM
CISA KEV No
Public POC No
EPSS 0.3%
Patch available Yes
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation
None
System Exposure· derived
Controlled
Automatable
No
Human Impact· derived
Medium
Technical Impact
Total

Priority Score

34
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +34
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

A buffer overflow occurs when a program writes more data to a memory buffer than it was allocated to hold, causing the excess data to spill into adjacent memory regions.

A stack-based buffer overflow occurs when a program writes more data to a buffer located on the stack than it was allocated to hold.

Remote Code Execution represents the critical moment when an attacker successfully runs arbitrary code on a target system without physical access.

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