How severe is CVE-2021-22699?

CVE-2021-22699 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2021-22699 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (58th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-22699?

CVE-2021-22699 primarily affects Schneider-electric Modicon M241 Firmware. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-22699?

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

When was CVE-2021-22699 published?

CVE-2021-22699 was published on 2021-05-26 and last updated on 2026-06-17.

CVE-2021-22699

CVE-2021-22699 is a high-severity vulnerability in Schneider-electric Modicon M241 Firmware with a CVSS 3.x base score of 7.5. 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-20.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 7.8
EPSS exploit prediction: 1% (58th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-20
Affected product: Schneider-electric Modicon M241 Firmware
Published: 2021-05-26
Last modified: 2026-06-17

Description

Improper Input Validation vulnerability exists in Modicon M241/M251 logic controllers firmware prior to V5.1.9.1 that could cause denial of service when specific crafted requests are sent to the controller over HTTP.

Frequently asked questions

What is CVE-2021-22699?: Improper Input Validation vulnerability exists in Modicon M241/M251 logic controllers firmware prior to V5.1.9.1 that could cause denial of service when specific crafted requests are sent to the controller over HTTP.
How severe is CVE-2021-22699?: CVE-2021-22699 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-22699 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (58th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-22699?: CVE-2021-22699 primarily affects Schneider-electric Modicon M241 Firmware. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-22699?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-22699 published?: CVE-2021-22699 was published on 2021-05-26 and last updated on 2026-06-17.

References

https://download.schneider-electric.com/files?p_Doc_Ref=SEVD-2021-130-05

Affected products (2)

cpe:2.3:o:schneider-electric:modicon_m241_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:schneider-electric:modicon_m251_firmware:*:*:*:*:*:*:*:*

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