CVE-2009-4893: Buffer overflow in UnrealIRCd 3.2beta11 through 3.2.8, when allow::options::noident is enabled, allows remote

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MEDIUM 6.8DOWNGRADE

CVE-2009-4893 is a medium-severity flaw (CVSS 6.8) affecting unrealircd. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Buffer overflow in UnrealIRCd 3.2beta11 through 3.2.8, when allow::options::noident is enabled, allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code via unspecified vectors.

Why this priority

No elevated risk signals yet

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	6.8 (Medium)
EPSS exploit chance	2.5% (top 15%)
CISA exploited list	No
Weakness	CWE-119
Published	2010-06-15
Last modified	2026-06-16

Publisher (CNA): Red Hat, Inc. · Vendor: unrealircd

Last updated 2026-06-16 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2010-06-15 14:04 UTCPublished CVE record published
2026-06-16 23:14 UTCUpdated Record last modified

unrealircd unrealircd DOWNGRADE

Affected: 3.2 beta11 · 3.2.1 · 3.2.1 pre1 · 3.2.1 pre2 · 3.2.2 · 3.2.2 pre1 · 3.2.3 · 3.2.3 pre1

Fixed in: no fixed release known

Safe to downgrade to: a release before 3.2

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 3.2 (Debian / Ubuntu)

apt-cache madison unrealircd sudo apt install unrealircd=<VERSION_BEFORE_3.2> sudo apt-mark hold unrealircd

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list unrealircd sudo dnf downgrade unrealircd-<VERSION_BEFORE_3.2> sudo dnf versionlock add unrealircd

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-2009-4893?

unrealircd: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2009-4893 being exploited?

CVE-2009-4893 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-2009-4893 affect?

CVE-2009-4893 affects unrealircd. Severity is medium (CVSS 6.8). Buffer overflow in UnrealIRCd 3.2beta11 through 3.2.8, when allow::options::noident is enabled, allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code via unspecified vectors.

How urgent is CVE-2009-4893?

Priority 45/100. No elevated risk signals yet.

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References

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