CVE-2021-40507: An issue was discovered in the ALU unit of the OR1200 (aka OpenRISC 1200) processor 2011-09-10 through 2015-11

Q: How do I fix CVE-2021-40507?

or1200 firmware: upgrade to newer than 2015-11-11. Exact commands for each OS are on this page.

Q: Is CVE-2021-40507 being exploited?

CVE-2021-40507 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-40507 affect?

CVE-2021-40507 affects or1200 firmware. Severity is 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 overflow flag is not being updated correctly for the subtract instruction, which results in an incorrect value in the ove

Q: How urgent is CVE-2021-40507?

Priority 53/100. Critical severity; Remotely exploitable, no login, no user action

This month

CRITICAL 9.8REMOTEUPGRADE

CVE-2021-40507 is a critical-severity flaw (CVSS 9.8) affecting or1200 firmware. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

Critical severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.7% (top 46%)
CISA exploited list	No
Weakness	CWE-287
Published	2023-04-18
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: openrisc

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2023-04-18 12:15 UTCPublished CVE record published
2026-06-17 04:07 UTCUpdated Record last modified

openrisc or1200 firmware UPGRADE

Affected: >= 2011-09-10 and <= 2015-11-11

Fixed in: newer than 2015-11-11

Safe to downgrade to: a release before 2011-09-10

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-40507?

or1200 firmware: upgrade to newer than 2015-11-11. Exact commands for each OS are on this page.

Is CVE-2021-40507 being exploited?

CVE-2021-40507 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-40507 affect?

CVE-2021-40507 affects or1200 firmware. Severity is 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 overflow flag is not being updated correctly for the subtract instruction, which results in an incorrect value in the ove

How urgent is CVE-2021-40507?

Priority 53/100. Critical severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2021-40506 CRITICAL 9.8 UPGRADE An issue was discovered in the ALU unit of the OR1200 (aka OpenRISC 1200) processor 2011-09-10 through 2015-11

References

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