How severe is CVE-2021-35474?

CVE-2021-35474 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-2021-35474 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (84th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-35474?

CVE-2021-35474 primarily affects Apache Traffic Server. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-35474?

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-2021-35474 published?

CVE-2021-35474 was published on 2021-06-30 and last updated on 2026-06-17.

CVE-2021-35474

CVE-2021-35474 is a critical-severity vulnerability in Apache Traffic Server 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-787.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 3% (84th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-787
Affected product: Apache Traffic Server
Published: 2021-06-30
Last modified: 2026-06-17

Description

Stack-based Buffer Overflow vulnerability in cachekey plugin of Apache Traffic Server. This issue affects Apache Traffic Server 7.0.0 to 7.1.12, 8.0.0 to 8.1.1, 9.0.0 to 9.0.1.

Frequently asked questions

What is CVE-2021-35474?: Stack-based Buffer Overflow vulnerability in cachekey plugin of Apache Traffic Server. This issue affects Apache Traffic Server 7.0.0 to 7.1.12, 8.0.0 to 8.1.1, 9.0.0 to 9.0.1.
How severe is CVE-2021-35474?: CVE-2021-35474 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-2021-35474 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (84th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-35474?: CVE-2021-35474 primarily affects Apache Traffic Server. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-35474?: 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-2021-35474 published?: CVE-2021-35474 was published on 2021-06-30 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:a:apache:traffic_server:*:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*

More vulnerabilities in Apache Traffic Server

CVE-2014-3525 — Critical (CVSS 10.0): Unspecified vulnerability in Apache Traffic Server 3.x through 3.2.5, 4.x before 4.2.1.1, and 5.x before 5.0.1 has…
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CVE-2020-1944 — Critical (CVSS 9.8): There is a vulnerability in Apache Traffic Server 6.0.0 to 6.2.3, 7.0.0 to 7.1.8, and 8.0.0 to 8.0.5 with a smuggling…
CVE-2019-17565 — Critical (CVSS 9.8): There is a vulnerability in Apache Traffic Server 6.0.0 to 6.2.3, 7.0.0 to 7.1.8, and 8.0.0 to 8.0.5 with a smuggling…
CVE-2019-17559 — Critical (CVSS 9.8): There is a vulnerability in Apache Traffic Server 6.0.0 to 6.2.3, 7.0.0 to 7.1.8, and 8.0.0 to 8.0.5 with a smuggling…
CVE-2015-3249 — Critical (CVSS 9.8): The HTTP/2 experimental feature in Apache Traffic Server 5.3.x before 5.3.1 allows remote attackers to cause a denial…

All CVEs affecting Apache Traffic Server →

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