How severe is CVE-2021-21135?

CVE-2021-21135 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 high, integrity none, and availability none.

Is CVE-2021-21135 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 19% (97th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-21135?

CVE-2021-21135 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-2021-21135?

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

When was CVE-2021-21135 published?

CVE-2021-21135 was published on 2021-02-09 and last updated on 2026-06-17.

CVE-2021-21135

CVE-2021-21135 is a medium-severity vulnerability in Google Chrome with a CVSS 3.x base score of 6.5. Its EPSS exploit-prediction score of 19% places it in the 97th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-346.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
CVSS v2: 4.3
EPSS exploit prediction: 19% (97th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-346
Affected product: Google Chrome
Published: 2021-02-09
Last modified: 2026-06-17

Description

Inappropriate implementation in Performance API in Google Chrome prior to 88.0.4324.96 allowed a remote attacker to leak cross-origin data via a crafted HTML page.

Frequently asked questions

What is CVE-2021-21135?: Inappropriate implementation in Performance API in Google Chrome prior to 88.0.4324.96 allowed a remote attacker to leak cross-origin data via a crafted HTML page.
How severe is CVE-2021-21135?: CVE-2021-21135 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 high, integrity none, and availability none.
Is CVE-2021-21135 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 19% (97th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-21135?: CVE-2021-21135 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-2021-21135?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-21135 published?: CVE-2021-21135 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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