What is CVE-2021-34550?

CVE-2021-34550 is a high-severity vulnerability in Torproject Tor, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 7.5/10. Published 2021-06-29.

How severe is CVE-2021-34550?

High severity. CVSS v3 base score is 7.5 out of 10.

Buffer overflow in Torproject Tor

CVE-2021-34550

An issue was discovered in Tor before 0.4.6.5, aka TROVE-2021-006. The v3 onion service descriptor parsing allows out-of-bounds memory access, and a client crash, via a crafted onion service descriptor

Vulnerability class: Buffer Overflow

Published 2021-06-29 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.016 (74.3th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 74th percentile — 74.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.016 · newest: 0.016 · change: 0.000

Affected products

Torproject Tor

Weakness classification (CWE)

CWE-119 — Improper Restriction of Operations within the Bounds of a Memory Buffer

References

gitlab.torproject.org/tpo/core/tor/-/issues/40392 (Broken Link)
blog.torproject.org/node/2041 (Release Notes, Vendor Advisory)
security.gentoo.org/glsa/202107-25 (vendor-advisory, Third Party Advisory)

Frequently asked questions

What is CVE-2021-34550?: CVE-2021-34550 is a high-severity vulnerability in Torproject Tor, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 7.5/10. Published 2021-06-29.
How severe is CVE-2021-34550?: High severity. CVSS v3 base score is 7.5 out of 10.