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Attack ChainAIDerived

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

  1. Access
    Gain privileged local access to platform
  2. Delivery
    Meet required firmware attack condition
  3. Exploit
    Supply crafted input to boot routine
  4. Execution
    Trigger integer overflow (CWE-190)
  5. Persist
    Corrupt firmware memory / execute code
  6. Impact
    Compromise boot chain and full system

Vulnerability Assessment

Weakness
CWE
ASVS 5.0
V15 - Secure Coding and Architecture Integer overflow checks
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

Exploitation requires local access to the platform (AV:L), pre-existing high privileges - a system-software adversary with a privileged user account (PR:H) - and a specific Attack Requirement to be satisfied (CVSS 4.0 AT:P), meaning a particular platform or firmware condition must be present for the overflow to be reachable; the exact condition is defined by Intel-SA-01425 and is not fully specified in the provided description. No user interaction is required (UI:N) and attack complexity is low (AC:L) once conditions are met. Limiting factors that reduce realistic risk: the attacker must already be privileged and local (no remote or unauthenticated path), the AT:P requirement means default/arbitrary configurations may not be exploitable, and only Intel platforms running Slim Bootloader firmware are affected.

Impact

The CVSS 4.0 base score is 8.7 (High) with vector AV:L/AC:L/AT:P/PR:H/UI:N and total impact (VC/VI/VA and SC/SI/SA all High). The signals are internally consistent toward a high-severity-but-hard-to-reach flaw: the impact is total, but the preconditions materially constrain real-world risk - the attacker must already hold high privileges (PR:H), have local access (AV:L), and a specific Attack Requirement must be met (AT:P). Corroborating this, EPSS is 0.01% (3rd percentile), SSVC reports Exploitation: none and Automatable: no, and there is no KEV listing and no known POC. In short, this is a genuinely serious firmware-integrity issue if reached, but it is not a mass-exploitation or wormable threat; it is a defense-in-depth / post-compromise concern rather than an internet-facing emergency. Note one caveat: SSVC rates Technical Impact as 'total' which aligns with the CVSS total-impact metrics, so there is no conflict, but the vendor advisory should be consulted to confirm the exact Attack Requirement (AT:P) since that condition governs realistic exploitability.

Exploit ScenarioDerived

A local attacker who already holds high (administrative/system) privileges on an Intel platform running Slim Bootloader targets a boot-time firmware routine, supplying crafted input that triggers the integer overflow when a required condition is present. The resulting memory corruption lets the attacker execute code in the firmware trust domain, corrupting the boot chain and gaining persistent, high-impact control over the system. No public POC is currently known, and the attack cannot be launched remotely or without existing privileges.

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
No patch listed yet 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – Jul 23, 2026

Escalation of privilege in Intel's Slim Bootloader UEFI firmware allows a privileged local adversary to trigger an integer overflow (CWE-190) and execute code within the firmware/boot context. Exploitation requires existing high privileges and local access with a specific attack requirement present, but a successful attack fully compromises confidentiality, integrity, and availability of both the vulnerable firmware and the subsequent system. There is no public exploit identified at time of analysis and EPSS probability is negligible (0.01%), consistent with SSVC exploitation status of 'none'.

RemediationAI

Consult Intel advisory Intel-SA-01425 (https://intel.com/content/www/us/en/security-center/advisory/intel-sa-01425.html) and update Slim Bootloader to the fixed firmware build published there; an exact fixed version is not stated in the provided data, so apply the patched release identified by Intel (Patch available per vendor advisory - released patched version not independently confirmed here). Because this is boot firmware, remediation means rebuilding/reflashing the platform firmware image and validating boot integrity afterward rather than a simple OS package update. Until the fixed build is deployed, reduce exposure to the required preconditions: restrict and audit privileged/administrative local access (the attack requires PR:H and local access), enforce firmware update signing and secure/verified boot, enable firmware write protection where supported, and use hardware/measured-boot attestation to detect tampering. These controls limit who can reach the vulnerable code path but do not remove the overflow, so applying the vendor firmware update remains the only complete fix; note that reflashing firmware carries operational risk and should be staged and tested to avoid bricking devices.

Affected VersionsENISA

Slim Bootloader may allow an escalation of privilege. System software adversary with a privileged user combined with a low complexity attack may enable local code execution. This result may potentially occur via local access when attack requirements are present without special internal knowledge and requires no user interaction. The potential vulnerability may impact the confidentiality (high), integrity (high) and availability (high) of the vulnerable system, resulting in subsequent system confidentiality (high), integrity (high) and availability (high) impacts. See references

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

Slim Bootloader is Intel's open-source, lightweight firmware boot solution (an alternative to full UEFI/coreboot stacks) used to initialize hardware and hand off to a payload/OS on Intel platforms. The root cause is CWE-190 (Integer Overflow or Wraparound): an arithmetic computation in the firmware - likely a size, length, or offset calculation during boot-time parsing or memory handling - wraps around its bounds, producing an undersized allocation or out-of-range access that can be steered into memory corruption. Because this executes in the pre-OS firmware trust domain, corruption there can undermine the platform's chain of trust and every layer that boots above it. The CPE string provided by the intel source is malformed (it embeds the full description as the product token: cpe:2.3:a:n/a:slim_bootloader...), so it does not reliably enumerate exact affected builds and should not be treated as authoritative version data.

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Severity by source

NVD PRIMARY 8.7 HIGH
CVSS:4.0/AV:L/AC:L/AT:P/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
vuln.today AI 7.5 HIGH

Local firmware flaw needing existing high privileges (PR:H) and a specific precondition (AC:H); firmware-to-system compromise crosses a trust boundary (S:C) with total C/I/A impact.

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

Primary rating from NVD.

CVSS VectorNVD

Attack Vector
Local
Attack Complexity
Low
Attack Requirements
Present
Privileges Required
High
User Interaction
None
Vulnerable system: Confidentiality
High
Vulnerable system: Integrity
High
Vulnerable system: Availability
High
Subsequent system: Confidentiality
High
Subsequent system: Integrity
High
Subsequent system: Availability
High

Lifecycle Timeline

3
CVSS changed
May 12, 2026 - 17:22 NVD
8.7 (HIGH)
CVE Published
May 12, 2026 - 16:34 nvd
HIGH 8.7
CVE Published
May 12, 2026 - 16:34 nvd
UNKNOWN (no severity yet)

DescriptionCVE.org

Integer overflow in the UEFI firmware for the Slim Bootloader may allow an escalation of privilege. System software adversary with a privileged user combined with a low complexity attack may enable local code execution. This result may potentially occur via local access when attack requirements are present without special internal knowledge and requires no user interaction. The potential vulnerability may impact the confidentiality (high), integrity (high) and availability (high) of the vulnerable system, resulting in subsequent system confidentiality (high), integrity (high) and availability (high) impacts.

Executive ViewAI

Why It Matters

Intel's Slim Bootloader contains a privilege escalation vulnerability (CVE-2026-20753, CVSS 8.7) affecting UEFI firmware. Exploitation requires an authenticated attacker with high privileges and local access to trigger an integer overflow, resulting in complete firmware and system compromise. Despite the severe technical impact, current exploitation probability is negligible (EPSS 0.0%), though organizations must account for this risk in environments facing insider threats or those with firmware attestation requirements.

Business Impact: High
Compensating Controls

No vendor-released patch identified at time of analysis. Interim mitigations: implement firmware integrity monitoring (TPM-based measurement, UEFI Secure Boot enforcement), restrict high-privilege local access through administrative account hardening, enable comprehensive audit logging of firmware operations, enforce physical/virtual security controls limiting local system access, and monitor for unauthorized firmware modifications.

Threat Intelligence Overview

EPSS Score
0.0%
Top 97% exploitable
Prevalence
Low
niche Intel open-source bootloader, limited to specific platform firmware builds
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 HIGH
CISA KEV No
Public POC No
EPSS 0.0%
Patch available No
Active threat No
Deciding rule
HIGH severity (CVSS 7.0-8.9)
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
Scheduled
Exploitation
None
System Exposure· derived
Small
Automatable
No
Human Impact
High
Technical Impact
Total

Priority Score

44
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +44
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Privilege escalation occurs when an attacker leverages flaws in access control mechanisms to gain permissions beyond what they were originally granted.

Integer overflow occurs when an arithmetic operation produces a result that exceeds the maximum value a given integer type can store.

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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