Is CVE-2021-40507 actively exploited?

No active exploitation of CVE-2021-40507 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2021-40507 be exploited remotely?

Yes. CVE-2021-40507 is exploitable remotely over the network (CVSS attack vector: Network).

What is the CVSS score of CVE-2021-40507?

CVE-2021-40507 has a CVSS score of 9.8 (CRITICAL).

HOME VULNERABILITIESCVE-2021-40507

CRITICAL

CVE-2021-40507

CWE-287Published: April 18, 2023· Updated: Jun 17, 2026

9.8

CVSS v3.1

Official Description

An issue was discovered in the ALU unit of the OR1200 (aka OpenRISC 1200) processor 2011-09-10 through 2015-11-11. The overflow flag is not being updated correctly for the subtract instruction, which results in an incorrect value in the overflow flag. Any software that relies on this flag may experience corruption in execution.

NVD Source

Risk Analysis

The OR1200 processor firmware contains a flaw in the ALU unit where the overflow flag is not updated correctly during subtraction. This can lead to incorrect execution and potential system corruption, warranting a critical severity rating. It is not currently in the CISA KEV.

There is no known public exploit for this vulnerability, and it is not in KEV. It is remotely exploitable with low attack complexity.

Recommended Action

Review firmware documentation for updates from the OpenRISC project. Implement software-level checks to validate arithmetic operations where possible.

Generated by the CTIWATCH analysis pipeline from this CVE's metadata (CVSS, EPSS, KEV status, exploit intelligence). Verify against vendor advisories before acting.

Technical Analysis

CVE-2021-40507 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 9.8.

From a weakness classification perspective (CWE-287): Authentication bypass vulnerabilities allow attackers to access protected resources without valid credentials.