No exploitation reportedFix available

CVE-2019-8955

Q: Is CVE-2019-8955 actively exploited?

Active exploitation of CVE-2019-8955 has not been confirmed. Its EPSS score was 4.6% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2019-8955?

CVE-2019-8955 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

No exploitation reported by the sources we read.

Published2019-02-21
Fixed in0.3.4.11 · 0.3.3.12
WeaknessCWE-770

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

In Tor before 0.3.3.12, 0.3.4.x before 0.3.4.11, 0.3.5.x before 0.3.5.8, and 0.4.x before 0.4.0.2-alpha, remote denial of service against Tor clients and relays can occur via memory exhaustion in the KIST cell scheduler.

Timeline

dates in UTC

2019-02-2123:29CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 18:48 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2019-8955?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2019-8955?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Torproject tor

Branch	Affected	Fixed in	Source
0.3	≥ 0.3.4.8, < 0.3.4.11	0.3.4.11	NVD
0.3	< 0.3.3.12	0.3.3.12	NVD
0.3	= 0.3.4.0	no fix published	NVD
0.3	= 0.3.4.1	no fix published	NVD
0.3	= 0.3.4.2	no fix published	NVD
0.3	= 0.3.4.3	no fix published	NVD
0.3	= 0.3.4.4	no fix published	NVD
0.3	= 0.3.4.5	no fix published	NVD
0.3	= 0.3.4.6	no fix published	NVD
0.3	= 0.3.4.7	no fix published	NVD
0.3	= 0.3.5.0	no fix published	NVD
0.3	= 0.3.5.1	no fix published	NVD

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Update Torproject tor to 0.3.4.11 · 0.3.3.12

Advisories and patches

blog.torproject.orgVendor Advisory
trac.torproject.orgVendor Advisory

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

NVDCVSS 3.07.5read 2026-10-23
NVDCVSS 2.05read 2026-10-23
NVDweakness (CWE)CWE-770read 2026-10-23
FIRST EPSSEPSS score4.6 %2026-10-22

Technical details

CVSS v3 Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Published: 2019-02-21
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2019-8955?

Is CVE-2019-8955 actively exploited?

Active exploitation of CVE-2019-8955 has not been confirmed. Its EPSS score was 4.6% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2019-8955?

CVE-2019-8955 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

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