How severe is CVE-2021-40507?

CVE-2021-40507 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-40507 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (50th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-40507?

CVE-2021-40507 affects Openrisc Or1200 Firmware. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-40507?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-40507 published?

CVE-2021-40507 was published on 2023-04-18 and last updated on 2026-06-17.

CVE-2021-40507

CVE-2021-40507 is a critical-severity vulnerability in Openrisc Or1200 Firmware with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-287.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
EPSS exploit prediction: 1% (50th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-287
Affected product: Openrisc Or1200 Firmware
Published: 2023-04-18
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2021-40507?: 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.
How severe is CVE-2021-40507?: CVE-2021-40507 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-40507 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (50th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-40507?: CVE-2021-40507 affects Openrisc Or1200 Firmware. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-40507?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-40507 published?: CVE-2021-40507 was published on 2023-04-18 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:o:openrisc:or1200_firmware:*:*:*:*:*:*:*:*

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CVE-2021-40506 — Critical (CVSS 9.8): An issue was discovered in the ALU unit of the OR1200 (aka OpenRISC 1200) processor 2011-09-10 through 2015-11-11. The…

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