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.

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.

This update for tor to version 0.3.4.11 fixes the following issues :

Security issue fixed :

  - CVE-2019-8955: Fixed a vulnerability in the KIST cell     scheduler which could lead to memory exhaustion and     finally Denial-of-Service (bsc#1126340).

update to latest upstream release (bz#1679732)

Note that Tenable Network Security has extracted the preceding description block directly from the Fedora update system website.
Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

ID	Name	Product	Family	Severity
183153	Ubuntu 16.04 ESM / 18.04 ESM / 20.04 ESM : Tor vulnerabilities (USN-5036-1)	Nessus	Ubuntu Local Security Checks	high
123654	openSUSE Security Update : tor (openSUSE-2019-1107)	Nessus	SuSE Local Security Checks	high
122560	Fedora 29 : tor (2019-55db688ba9)	Nessus	Fedora Local Security Checks	high
122559	Fedora 28 : tor (2019-2f47af13f6)	Nessus	Fedora Local Security Checks	high

Detections

Analytics

CVE-2019-8955

high

Tenable Plugins

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