CVE-2020-8443: In OSSEC-HIDS 2.7 through 3.5.0, the server component responsible for log analysis (ossec-analysisd) is vulner

This week

CRITICAL 9.8REMOTEUPGRADE

CVE-2020-8443 is a critical-severity flaw (CVSS 9.8) affecting ossec. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

In OSSEC-HIDS 2.7 through 3.5.0, the server component responsible for log analysis (ossec-analysisd) is vulnerable to an off-by-one heap-based buffer overflow during the cleaning of crafted syslog msgs (received from authenticated remote agents and delivered to the analysisd processing queue by ossec-remoted).

Why this priority

Critical severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	2.7% (top 14%)
CISA exploited list	No
Weakness	CWE-193, CWE-787
Published	2020-01-30
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: ossec

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2020-01-30 01:15 UTCPublished CVE record published
2026-06-17 03:26 UTCUpdated Record last modified

ossec ossec UPGRADE

Affected: >= 2.7 and <= 3.5.0

Fixed in: newer than 3.5.0

Safe to downgrade to: a release before 2.7

1. Check installed version

apt-cache policy ossec || rpm -q ossec || ossec --version

2. UPGRADE to newer than 3.5.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade ossec

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade ossec

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 2.7 (Debian / Ubuntu)

apt-cache madison ossec sudo apt install ossec=<VERSION_BEFORE_2.7> sudo apt-mark hold ossec

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list ossec sudo dnf downgrade ossec-<VERSION_BEFORE_2.7> sudo dnf versionlock add ossec

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2020-8443?

ossec: upgrade to newer than 3.5.0. Exact commands for each OS are on this page.

Is CVE-2020-8443 being exploited?

CVE-2020-8443 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2020-8443 affect?

CVE-2020-8443 affects ossec. Severity is critical (CVSS 9.8). In OSSEC-HIDS 2.7 through 3.5.0, the server component responsible for log analysis (ossec-analysisd) is vulnerable to an off-by-one heap-based buffer overflow during the cleaning of crafted syslog msgs (received from authenticated remote ag

How urgent is CVE-2020-8443?

Priority 66/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2021-28040 HIGH 7.5 DOWNGRADE An issue was discovered in OSSEC 3.6.0
CVE-2020-8448 MEDIUM 5.5 UPGRADE In OSSEC-HIDS 2.7 through 3.5.0, the server component responsible for log analysis (ossec-analysisd) is vulner
CVE-2020-8447 CRITICAL 9.8 UPGRADE In OSSEC-HIDS 2.7 through 3.5.0, the server component responsible for log analysis (ossec-analysisd) is vulner
CVE-2020-8446 MEDIUM 5.5 UPGRADE In OSSEC-HIDS 2.7 through 3.5.0, the server component responsible for log analysis (ossec-analysisd) is vulner
CVE-2020-8445 CRITICAL 9.8 UPGRADE In OSSEC-HIDS 2.7 through 3.5.0, the OS_CleanMSG function in ossec-analysisd doesn't remove or encode terminal

References

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