CVE-2023-4491: Buffer overflow vulnerability in Easy Address Book Web Server 1.6 version

This month

CRITICAL 9.8REMOTEDOWNGRADE

CVE-2023-4491 is a critical-severity flaw (CVSS 9.8) affecting easy address book web server. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Buffer overflow vulnerability in Easy Address Book Web Server 1.6 version. The exploitation of this vulnerability could allow an attacker to send a very long username string to /searchbook.ghp, asking for the name via a POST request, resulting in arbitrary code execution on the remote machine.

Why this priority

Critical severity
Remotely exploitable, no login, no user action

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

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.0% (top 38%)
CISA exploited list	No
Weakness	CWE-119
Published	2023-10-04
Last modified	2026-06-17

Publisher (CNA): Spanish National Cybersecurity Institute, S.A. (INCIBE) · Vendor: easy address book web server project

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

Am I affected?

Timeline

2023-10-04 13:15 UTCPublished CVE record published
2026-06-17 06:37 UTCUpdated Record last modified

easy address book web server project easy address book web server DOWNGRADE

Affected: 1.6

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.6

1. Check installed version

apt-cache policy easy-address-book-web-server || rpm -q easy-address-book-web-server || easy-address-book-web-server --version

2. No fixed release: DOWNGRADE to a release before 1.6 (Debian / Ubuntu)

apt-cache madison easy-address-book-web-server sudo apt install easy-address-book-web-server=<VERSION_BEFORE_1.6> sudo apt-mark hold easy-address-book-web-server

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

dnf --showduplicates list easy-address-book-web-server sudo dnf downgrade easy-address-book-web-server-<VERSION_BEFORE_1.6> sudo dnf versionlock add easy-address-book-web-server

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-2023-4491?

easy address book web server: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2023-4491 being exploited?

CVE-2023-4491 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-2023-4491 affect?

CVE-2023-4491 affects easy address book web server. Severity is critical (CVSS 9.8). Buffer overflow vulnerability in Easy Address Book Web Server 1.6 version. The exploitation of this vulnerability could allow an attacker to send a very long username string to /searchbook.ghp, asking for the name via a POST request, result

How urgent is CVE-2023-4491?

Priority 55/100. Critical severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2023-4493 MEDIUM 6.1 DOWNGRADE Stored Cross-Site Scripting in Easy Address Book Web Server 1.6 version, through the users_admin.ghp file that
CVE-2023-4492 MEDIUM 6.1 DOWNGRADE Vulnerability in Easy Address Book Web Server 1.6 version, affecting the parameters (firstname, homephone, las
CVE-2006-4654 MEDIUM 5.1 DOWNGRADE Format string vulnerability in Easy Address Book Web Server 1.2 allows remote attackers to cause a denial of s

References

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