Ubuntu 16.04 ESM / 18.04 ESM / 20.04 ESM : Tor vulnerabilities (USN-5036-1)

high Nessus Plugin ID 183153


The remote Ubuntu host is missing one or more security updates.


The remote Ubuntu 16.04 ESM / 18.04 ESM / 20.04 ESM host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-5036-1 advisory.

- In Tor before, 0.3.4.x before, 0.3.5.x before, and 0.4.x before, remote denial of service against Tor clients and relays can occur via memory exhaustion in the KIST cell scheduler. (CVE-2019-8955)

- Tor before allows a remote participant in the Tor directory protocol to exhaust CPU resources on a target, aka TROVE-2021-001. (CVE-2021-28089)

- Tor before allows a remote attacker to cause Tor directory authorities to exit with an assertion failure, aka TROVE-2021-002. (CVE-2021-28090)

- An issue was discovered in Tor before, aka TROVE-2021-003. An attacker can forge RELAY_END or RELAY_RESOLVED to bypass the intended access control for ending a stream. (CVE-2021-34548)

- An issue was discovered in Tor before, aka TROVE-2021-005. Hashing is mishandled for certain retrieval of circuit data. Consequently. an attacker can trigger the use of an attacker-chosen circuit ID to cause algorithm inefficiency. (CVE-2021-34549)

- An issue was discovered in Tor before, 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 (CVE-2021-34550)

- Tor before,, and mishandles the relationship between batch-signature verification and single-signature verification, leading to a remote assertion failure, aka TROVE-2021-007.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.


Update the affected tor and / or tor-geoipdb packages.

See Also


Plugin Details

Severity: High

ID: 183153

File Name: ubuntu_USN-5036-1.nasl

Version: 1.0

Type: local

Agent: unix

Published: 10/16/2023

Updated: 10/16/2023

Supported Sensors: Agentless Assessment, Frictionless Assessment Agent, Frictionless Assessment AWS, Frictionless Assessment Azure, Nessus Agent, Nessus

Risk Information


Risk Factor: Medium

Score: 4.4


Risk Factor: Medium

Base Score: 5

Temporal Score: 3.9

Vector: CVSS2#AV:N/AC:L/Au:N/C:N/I:N/A:P

CVSS Score Source: CVE-2021-38385


Risk Factor: High

Base Score: 7.5

Temporal Score: 6.7

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Temporal Vector: CVSS:3.0/E:P/RL:O/RC:C

Vulnerability Information

CPE: p-cpe:/a:canonical:ubuntu_linux:tor, cpe:/o:canonical:ubuntu_linux:16.04:-:esm, p-cpe:/a:canonical:ubuntu_linux:tor-geoipdb, cpe:/o:canonical:ubuntu_linux:20.04:-:esm, cpe:/o:canonical:ubuntu_linux:18.04:-:esm

Required KB Items: Host/cpu, Host/Ubuntu, Host/Ubuntu/release, Host/Debian/dpkg-l

Exploit Available: true

Exploit Ease: Exploits are available

Patch Publication Date: 10/4/2022

Vulnerability Publication Date: 2/21/2019

Reference Information

CVE: CVE-2019-8955, CVE-2021-28089, CVE-2021-28090, CVE-2021-34548, CVE-2021-34549, CVE-2021-34550, CVE-2021-38385

USN: 5036-1