Security Hardening

Common Problems 117518

Ubuntu 20.04 LTS – SSH login fails with Permission denied (publickey)

🟠 High   ⏱ 5–30 min  Last verified: 27 May 2021 Affected versions: Ubuntu 20.04 LTS Ubuntu 20.04 Ubuntu 20.04.6 📖 ~1 min read Table of contents Symptom & Impact Environment & Reproduction Root Cause Analysis Quick Triage Step-by-Step Diagnosis Solution – Primary Fix Solution – Alternative Approaches Verification & Acceptance Criteria Rollback Plan Prevention […]

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FreeBSD 13 — py33-radicale — multiple vulnerabilities (2 CVEs) — patch and remediation guide — diagnosis and fix on FreeBSD 13

FreeBSD 13 — py33-radicale — multiple vulnerabilities (2 CVEs) — patch and remediation guide

🟢 Low   ⏱ 5–15 min  Last verified: 27 May 2021 Affected versions: FreeBSD 13 📖 ~4 min read  •  Source: FreeBSD VuXML VuXML topic: radicale — multiple vulnerabilities Related CVEs: CVE-2015-8747 CVE-2015-8748 Upstream summary: Radicale reports: The multifilesystem backend allows access to arbitrary files on all platforms. Prevent regex injection in rights management. Table […]

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FreeBSD 13 — libxfce4gui — multiple vulnerabilities (2 CVEs) — patch and remediation guide — diagnosis and fix on FreeBSD 13

FreeBSD 13 — libxfce4gui — multiple vulnerabilities (2 CVEs) — patch and remediation guide

🟢 Low   ⏱ 5–15 min  Last verified: 27 May 2021 Affected versions: FreeBSD 13 📖 ~4 min read  •  Source: FreeBSD VuXML VuXML topic: xfce — multiple vulnerabilities Related CVEs: CVE-2007-6531 CVE-2007-6532 Upstream summary: Gentoo reports: A remote attacker could entice a user to install a specially crafted "rc" file to execute arbitrary code […]

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Alpine Linux edge — lz4 — multiple vulnerabilities (2 CVEs) — patch and remediation guide — diagnosis and fix on Alpine Linux edge

Alpine Linux edge — lz4 — multiple vulnerabilities (2 CVEs) — patch and remediation guide

🟡 Medium   ⏱ 10–30 min  Last verified: 25 May 2026 Affected versions: Alpine Linux edge / fixed in 1.9.3-r1 📖 ~4 min read  •  Source: Alpine secdb entry — lz4 1.9.3-r1 Related CVEs: CVE-2021-3520 CVE-2019-17543 Upstream summary: Alpine main repository for vedge ships lz4 1.9.3-r1 which addresses CVE-2021-3520. Table of contents Symptom & Impact […]

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FreeBSD 13 — ppxp — vulnerability — patch and remediation guide — diagnosis and fix on FreeBSD 13

FreeBSD 13 — ppxp — vulnerability — patch and remediation guide

🟢 Low   ⏱ 5–15 min  Last verified: 27 May 2021 Affected versions: FreeBSD 13 📖 ~4 min read  •  Source: FreeBSD VuXML VuXML topic: ppxp — local root exploit Related CVEs: CVE-2005-0392 Upstream summary: A Debian Advisory reports: Jens Steube discovered that ppxp, yet another PPP program, does not release root privileges when opening […]

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Ubuntu 18.04 — fail2ban — vulnerability — patch and remediation guide — diagnosis and fix on Ubuntu 18.04

Ubuntu 18.04 — fail2ban — vulnerability — patch and remediation guide

🟢 Low   ⏱ 5–15 min  Last verified: 27 May 2021 Affected versions: Ubuntu 18.04 (bionic) 📖 ~4 min read  •  Source: Ubuntu Security Notice USN-5232-1 Related CVEs: CVE-2021-32749 Upstream summary: Jakub Żoczek discovered that certain Fail2ban actions handled whois responses in an insecure way. If Fail2ban was configured to use certain mail actions like […]

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Common Problems 113623

Windows Server 2012 R2 — Windows Update and web traffic fail due to bad proxy PAC settings — Fix & Prevention

🟡 Medium   ⏱ 5–30 min  Last verified: 27 May 2021 Affected versions: Windows Server 2012 R2 📖 ~1 min read Table of contents Symptom & Impact Environment & Reproduction Root Cause Analysis Quick Triage Step-by-Step Diagnosis Solution — Primary Fix Solution — Alternative Approaches Verification & Acceptance Criteria Rollback Plan Prevention & Hardening Related […]

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Amazon Linux 2 — python3-pygments — vulnerability — patch and remediation guide — diagnosis and fix on Amazon Linux 2

Amazon Linux 2 — python3-pygments — vulnerability — patch and remediation guide

🟡 Medium   ⏱ 10–30 min  Last verified: 25 May 2026 Affected versions: Amazon Linux 2 📖 ~4 min read  •  Source: Amazon Linux advisory ALAS2-2023-2117 Related CVEs: CVE-2021-27291 Upstream summary: In pygments 1.1+, fixed in 2.7.4, the lexers used to parse programming languages rely heavily on regular expressions. Some of the regular expressions have […]

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Oracle Linux 8 — httpd:2.4 — vulnerability — patch and remediation guide — diagnosis and fix on Oracle Linux 8

Oracle Linux 8 — httpd:2.4 — vulnerability — patch and remediation guide (ELSA-2022-0891)

🟡 Medium   ⏱ 10–30 min  Last verified: 27 May 2021 Affected versions: Oracle Linux 8 📖 ~4 min read  •  Source: ELSA advisory ELSA-2022-0891 Related CVEs: CVE-2021-34798 CVE-2021-39275 Table of contents Symptom & Impact Environment & Reproduction Root Cause Analysis Quick Triage Step-by-Step Diagnosis Solution – Primary Fix Solution – Alternative Approaches Verification & […]

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CHAT