CVE-2021-43614: H2O buffer overflow

CISO Take

This is a buffer overflow in how InsydeH2O UEFI firmware parses the PlatformLangCodes NVRAM variable, causing resource exhaustion and device failure — a firmware-level denial-of-service bug, not a vulnerability in any tracked AI/ML software package. Exploitation requires physical access, high attacker privileges, high attack complexity, and user interaction, and its EPSS score of 0.13% indicates a near-negligible real-world exploitation probability; it is absent from CISA KEV and has no public exploit or Nuclei template. The 'ml_library' AI-category tag on this CVE appears to be a data classification artifact: InsydeH2O is BIOS/UEFI firmware shipped on laptops and servers, it doesn't match any entry in our AI package catalog, and the description contains no AI/ML-specific context. The only residual relevance for a CISO is asset-inventory hygiene — if InsydeH2O-based hardware underlies edge AI inference appliances or on-prem GPU servers, an attacker with sustained physical access could crash the device and degrade availability of whatever workload runs on it. Action: track this via standard firmware/BIOS patch management rather than the AI vulnerability pipeline, apply the Insyde vendor advisory (SA-2022026) when updating firmware, and rely on physical-access controls as the primary mitigation since no software workaround exists.

Sources:NVDEPSSOpenSSFinsyde.com

What is the risk?

Low practical risk. The CVSS 6.7 (medium) score is driven by high confidentiality/integrity impact and low availability impact, but the attack vector (physical), high complexity, high privileges required, and mandatory user interaction sharply constrain real-world exploitability. EPSS of 0.00131 (0.13%) reflects negligible observed exploitation activity in the wild. No KEV listing, no public PoC, no scanner coverage. Package risk score of 0/100 and no CWE assigned further support a low-severity operational posture — this is a narrow, hardware-adjacent bug rather than a network-exploitable or remotely reachable flaw.

How does the attack unfold?

Physical Access

Adversary gains sustained physical access to the target device and the high privileges needed to modify UEFI settings.

AML.T0041

Malformed Variable Injection

Adversary sets a malformed value for the PlatformLangCodes UEFI NVRAM variable, requiring user interaction (e.g., a reboot) to trigger parsing.

Resource Exhaustion / Crash

The firmware's buffer overflow while parsing the variable exhausts system resources, causing the device to fail and lose availability.

Physical Access

Adversary gains sustained physical access to the target device and the high privileges needed to modify UEFI settings.

AML.T0041

Malformed Variable Injection

Adversary sets a malformed value for the PlatformLangCodes UEFI NVRAM variable, requiring user interaction (e.g., a reboot) to trigger parsing.

Resource Exhaustion / Crash

The firmware's buffer overflow while parsing the variable exhausts system resources, causing the device to fail and lose availability.

What systems are affected?

Package	Ecosystem	Vulnerable Range	Patched
H2O	pip	—	No patch
7.5KOpenSSF 5.727 dependentsPushed 11d ago8% patched~0d to patchFull package profile →

Do you use H2O? You're affected.

How severe is it?

CVSS 3.1

6.7 / 10

EPSS

0.2%

chance of exploitation in 30 days

Higher than 4% of all CVEs

Source: EPSS v3 — FIRST.org

Exploitation Status

No known exploitation

Sophistication

Moderate

What is the attack surface?

AVPhysical

ACHigh

PRHigh

UIRequired

SChanged

CHigh

IHigh

ALow

What should I do?

1 step

1) Do not route this through AI-stack patch workflows — treat it as standard firmware/BIOS asset management. 2) Inventory devices running InsydeH2O UEFI firmware, prioritizing any that host AI inference/edge appliances or GPU servers. 3) Apply the vendor fix referenced in Insyde Security Pledge SA-2022026 (https://www.insyde.com/security-pledge/sa-2022026/) once available for the affected firmware build. 4) Since exploitation requires physical access and high privileges, enforce physical security controls (locked racks/enclosures, BIOS/UEFI admin passwords, Secure Boot, disabled unauthorized USB boot) rather than relying on a software-only fix. 5) No detection signature is applicable given the local/physical nature of the attack; monitor for unexpected device reboots/crashes as a general indicator.

What does CISA's SSVC say?

DecisionTrack

Exploitationnone

AutomatableNo

Technical Impacttotal

Source: CISA Vulnrichment (SSVC v2.0). Decision based on the CISA Coordinator decision tree.

How is it classified?

DoSInferenceAML.T0041- Physical Environment Access

Which compliance frameworks are affected?

Compliance analysis pending. Sign in for full compliance mapping when available.

Frequently Asked Questions

What is CVE-2021-43614?

This is a buffer overflow in how InsydeH2O UEFI firmware parses the PlatformLangCodes NVRAM variable, causing resource exhaustion and device failure — a firmware-level denial-of-service bug, not a vulnerability in any tracked AI/ML software package. Exploitation requires physical access, high attacker privileges, high attack complexity, and user interaction, and its EPSS score of 0.13% indicates a near-negligible real-world exploitation probability; it is absent from CISA KEV and has no public exploit or Nuclei template. The 'ml_library' AI-category tag on this CVE appears to be a data classification artifact: InsydeH2O is BIOS/UEFI firmware shipped on laptops and servers, it doesn't match any entry in our AI package catalog, and the description contains no AI/ML-specific context. The only residual relevance for a CISO is asset-inventory hygiene — if InsydeH2O-based hardware underlies edge AI inference appliances or on-prem GPU servers, an attacker with sustained physical access could crash the device and degrade availability of whatever workload runs on it. Action: track this via standard firmware/BIOS patch management rather than the AI vulnerability pipeline, apply the Insyde vendor advisory (SA-2022026) when updating firmware, and rely on physical-access controls as the primary mitigation since no software workaround exists.

Is CVE-2021-43614 actively exploited?

No confirmed active exploitation of CVE-2021-43614 has been reported, but organizations should still patch proactively.

How to fix CVE-2021-43614?

1) Do not route this through AI-stack patch workflows — treat it as standard firmware/BIOS asset management. 2) Inventory devices running InsydeH2O UEFI firmware, prioritizing any that host AI inference/edge appliances or GPU servers. 3) Apply the vendor fix referenced in Insyde Security Pledge SA-2022026 (https://www.insyde.com/security-pledge/sa-2022026/) once available for the affected firmware build. 4) Since exploitation requires physical access and high privileges, enforce physical security controls (locked racks/enclosures, BIOS/UEFI admin passwords, Secure Boot, disabled unauthorized USB boot) rather than relying on a software-only fix. 5) No detection signature is applicable given the local/physical nature of the attack; monitor for unexpected device reboots/crashes as a general indicator.

What systems are affected by CVE-2021-43614?

This vulnerability affects the following AI/ML architecture patterns: model serving.

What is the CVSS score for CVE-2021-43614?

CVE-2021-43614 has a CVSS v3.1 base score of 6.7 (MEDIUM). The EPSS exploitation probability is 0.15%.

What is the AI security impact?

Affected AI Architectures

model serving

MITRE ATLAS Techniques

AML.T0041Physical Environment Access

What are the technical details?

Original Advisory

Error in handling the PlatformLangCodes UEFI variable could cause a buffer overflow, leading to resource exhaustion and failure.

Exploitation Scenario

An adversary with physical access to a device (e.g., an on-prem AI inference server or edge appliance in a shared facility) and elevated local privileges crafts a malformed value for the PlatformLangCodes UEFI variable, then triggers a user-interaction step (such as a reboot or firmware settings change) that causes the firmware to parse the corrupted variable. The resulting buffer overflow exhausts firmware-level resources, crashing the device and denying availability of any AI service hosted on it until the device is recovered or reflashed. Given the high complexity and privilege/access requirements, this is realistic mainly as an insider-threat or physical-security-breach scenario rather than a remote attack.