How severe is CVE-2021-21139?

CVE-2021-21139 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity high, and availability none.

Is CVE-2021-21139 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 5% (91st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-21139?

CVE-2021-21139 primarily affects Google Chrome. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-21139?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-21139 published?

CVE-2021-21139 was published on 2021-02-09 and last updated on 2026-06-17.

CVE-2021-21139

CVE-2021-21139 is a medium-severity vulnerability in Google Chrome with a CVSS 3.x base score of 6.5. 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-1021.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
CVSS v2: 4.3
EPSS exploit prediction: 5% (91st percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-1021
Affected product: Google Chrome
Published: 2021-02-09
Last modified: 2026-06-17

Description

Inappropriate implementation in iframe sandbox in Google Chrome prior to 88.0.4324.96 allowed a remote attacker to bypass navigation restrictions via a crafted HTML page.

Frequently asked questions

What is CVE-2021-21139?: Inappropriate implementation in iframe sandbox in Google Chrome prior to 88.0.4324.96 allowed a remote attacker to bypass navigation restrictions via a crafted HTML page.
How severe is CVE-2021-21139?: CVE-2021-21139 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity high, and availability none.
Is CVE-2021-21139 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 5% (91st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-21139?: CVE-2021-21139 primarily affects Google Chrome. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-21139?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-21139 published?: CVE-2021-21139 was published on 2021-02-09 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:a:google:chrome:*:*:*:*:*:*:*:*
cpe:2.3:a:microsoft:edge_chromium:*:*:*:*:*:*:*:*

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