An issue was discovered in Tor before 0.4.6.5, 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.

There are packages installed that are affected by multiple vulnerabilities referenced in the following CVEs:

  - Acrobat Reader DC versions versions 2021.001.20150 (and earlier), 2020.001.30020 (and earlier) and
    2017.011.30194 (and earlier) are affected by a Use After Free vulnerability. An unauthenticated attacker
    could leverage this vulnerability to achieve arbitrary code execution in the context of the current user.
    Exploitation of this issue requires user interaction in that a victim must open a malicious file.
    (CVE-2021-28550)

  - Tor before 0.3.5.10, 0.4.x before 0.4.1.9, and 0.4.2.x before 0.4.2.7 allows remote attackers to cause a
    Denial of Service (CPU consumption), aka TROVE-2020-002. (CVE-2020-10592)

  - Tor before 0.3.5.10, 0.4.x before 0.4.1.9, and 0.4.2.x before 0.4.2.7 allows remote attackers to cause a
    Denial of Service (memory leak), aka TROVE-2020-004. This occurs in circpad_setup_machine_on_circ because
    a circuit-padding machine can be negotiated twice on the same circuit. (CVE-2020-10593)

  - Tor before 0.4.5.7 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 0.4.5.7 allows a remote attacker to cause Tor directory authorities to exit with an assertion
    failure, aka TROVE-2021-002. (CVE-2021-28090)

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.

    It was discovered that Tor incorrectly handled certain memory operations. A remote attacker could use this     issue to cause a denial of service. This issue only affected Ubuntu 18.04 ESM. (CVE-2019-8955)

    It was discovered that Tor did not properly handle the input length to dump_desc() function. A remote     attacker could use this issue to cause a denial of service. This issue only affected Ubuntu 16.04 ESM,     Ubuntu 18.04 ESM and Ubuntu 20.04 ESM. (CVE-2021-28089)

    It was discovered that Tor did not properly sanitize the relay nickname in     dirvote_add_signatures_to_pending_consensus() function. An attacker could possibly use this issue to cause     an assertion failure and then cause a denial of service. (CVE-2021-28090)

    It was discovered that Tor did not properly validate the layer hint on half-open streams. A remote     attacker could possibly use this issue to bypass the access control, leading to remote code execution.
    This issue only affected Ubuntu 20.04 ESM. (CVE-2021-34548)

    It was discovered that Tor was using an insecure hash function. A remote attacker could use this issue to     cause a denial of service. This issue only affected Ubuntu 16.04 ESM, Ubuntu 18.04 ESM and Ubuntu 20.04     ESM. (CVE-2021-34549)

    It was discovered that Tor did not properly manage memory under certain circumstances. If a user were     tricked into opening a specially crafted request, a remote attacker could possibly use this issue to cause     a crash, resulting in a denial of service, or possibly reading sensitive data. This issue only affected     Ubuntu 18.04 ESM and Ubuntu 20.04 ESM. (CVE-2021-34550)

    It was discovered that Tor mishandles the relationship between batch-signature verification and single-     signature verification. An attacker could possibly use this issue to cause an assertion failure and then     cause a denial of service. This issue only affected Ubuntu 16.04 ESM, Ubuntu 18.04 ESM and Ubuntu 20.04     ESM. (CVE-2021-38385)

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

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

The remote host is affected by the vulnerability described in GLSA-202107-25 (Tor: Multiple vulnerabilities)

    Multiple vulnerabilities have been discovered in Tor. Please review the       CVE identifiers referenced below for details.
  Impact :

    Please review the referenced CVE identifiers for details.
  Workaround :

    There is no known workaround at this time.

The remote SUSE Linux SUSE15 host has a package installed that is affected by multiple vulnerabilities as referenced in the openSUSE-SU-2021:0926-1 advisory. Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

Multiple security vulnerabilities were discovered in Tor, a connection-based low-latency anonymous communication system, which could result in denial of service or spoofing.

ID	Name	Product	Family	Severity
407405	Alpine: multiple tor packages: security update to 0.4.4.9-r0	Tenable Cloud Security	Alpine Linux Local Security Checks	high
407405	Alpine: multiple tor packages: security update to 0.4.4.9-r0	Tenable Self-Hosted Container Security	Alpine Linux Local Security Checks	high
183153	Ubuntu 16.04 ESM / 18.04 ESM / 20.04 ESM : Tor vulnerabilities (USN-5036-1)	Nessus	Ubuntu Local Security Checks	high
157031	GLSA-202107-25 : Tor: Multiple vulnerabilities	Nessus	Gentoo Local Security Checks	high
151065	openSUSE 15 Security Update : tor (openSUSE-SU-2021:0926-1)	Nessus	SuSE Local Security Checks	high
150903	Debian DSA-4932-1 : tor - security update	Nessus	Debian Local Security Checks	high

Detections

Analytics

CVE-2021-34549

high

Tenable Plugins

high

high

high

high

high

high