What is CVE-2021-35474?

CVE-2021-35474 is a critical-severity vulnerability in Apache Traffic Server, classified under Stack-based Buffer Overflow. CVSS score: 9.8/10. Published 2021-06-30.

How severe is CVE-2021-35474?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Buffer overflow in Apache Traffic Server

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.

Vulnerability class: Buffer Overflow

Published 2021-06-30 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.027 (85.9th percentile), scored 2026-10-22.

Low probability of exploitation in the next 30 days, but still tracked. 86th percentile — 85.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.027 · newest: 0.027 · change: 0.000

Affected products

Apache Traffic Server
Apache Software Foundation Traffic Server — versions Apache Traffic Server 7.0.0 to 7.1.12, 8.0.0 to 8.1.1, 9.0.0 to 9.0.1
Debian Linux — versions 10.0

Weakness classification (CWE)

References

lists.apache.org/thread.html/ra1a41ff92a70d25bf576d7da2590575e8ff430393a3f4a0c3… (Mailing List, Vendor Advisory)
www.debian.org/security/2021/dsa-4957 (vendor-advisory, Third Party Advisory)

Frequently asked questions

What is CVE-2021-35474?: CVE-2021-35474 is a critical-severity vulnerability in Apache Traffic Server, classified under Stack-based Buffer Overflow. CVSS score: 9.8/10. Published 2021-06-30.
How severe is CVE-2021-35474?: Critical severity. CVSS v3 base score is 9.8 out of 10.