CVE-2004-0594: The memory_limit functionality in PHP 4.x up to 4.3.7, and 5.x up to 5.0.0RC3, under certain conditions such a

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MEDIUM 5.1WATCHLISTDOWNGRADEMITIGATEMITIGATE

CVE-2004-0594 is a medium-severity flaw (CVSS 5.1) affecting openpkg, converged communications server, debian linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The memory_limit functionality in PHP 4.x up to 4.3.7, and 5.x up to 5.0.0RC3, under certain conditions such as when register_globals is enabled, allows remote attackers to execute arbitrary code by triggering a memory_limit abort during execution of the zend_hash_init function and overwriting a HashTable destructor pointer before the initialization of key data structures is complete.

Why this priority

EPSS top 1%: very likely to be exploited
Public exploit reference
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	5.1 (Medium)
EPSS exploit chance	54.9% (top 1%)
CISA exploited list	No
Weakness	CWE-367
Published	2004-07-27
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: avaya · debian · hp · openpkg · php · trustix

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

Am I affected?

Timeline

2004-07-27 04:00 UTCPublished CVE record published
2026-06-16 22:05 UTCUpdated Record last modified

openpkg openpkg DOWNGRADE

Affected: 2.0 · 2.1

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.0

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 2.0 (Debian / Ubuntu)

apt-cache madison openpkg sudo apt install openpkg=<VERSION_BEFORE_2.0> sudo apt-mark hold openpkg

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

dnf --showduplicates list openpkg sudo dnf downgrade openpkg-<VERSION_BEFORE_2.0> sudo dnf versionlock add openpkg

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.

avaya converged communications server MITIGATE

Affected: 2.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.0

Firmware

Install the latest firmware from the vendor advisory; if none, apply the vendor workaround.

debian debian linux MITIGATE

Affected: 3.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 3.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

hp hp-ux MITIGATE

Affected: b.11.00 · b.11.11 · b.11.22 · b.11.23

Fixed in: no fixed release known

Safe to downgrade to: a release before b.11.00

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

trustix secure linux MITIGATE

Affected: 1.5 · 2.0 · 2.1

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.5

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

php php UPGRADE

Affected: >= 4.0 and < 4.3.7 · 5.0.0 beta1 · 5.0.0 beta2 · 5.0.0 beta3 · 5.0.0 beta4 · 5.0.0 rc1 · 5.0.0 rc2

Fixed in: 4.3.7

Safe to downgrade to: a release before 4.0

1. Check installed version

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

2. UPGRADE to 4.3.7 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade php

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 4.0 (Debian / Ubuntu)

apt-cache madison php sudo apt install php=<VERSION_BEFORE_4.0> sudo apt-mark hold php

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

dnf --showduplicates list php sudo dnf downgrade php-<VERSION_BEFORE_4.0> sudo dnf versionlock add php

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.

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Exploit-DB: PHP 4.3.7/5.0.0RC3 - 'memory_limit' Remote Overflow

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-2004-0594?

openpkg: downgrade or apply the listed mitigation; converged communications server: mitigate or apply the listed mitigation; debian linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2004-0594 being exploited?

CVE-2004-0594 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-2004-0594 affect?

CVE-2004-0594 affects openpkg, converged communications server, debian linux. Severity is medium (CVSS 5.1). The memory_limit functionality in PHP 4.x up to 4.3.7, and 5.x up to 5.0.0RC3, under certain conditions such as when register_globals is enabled, allows remote attackers to execute arbitrary code by triggering a memory_limit abort during ex

How urgent is CVE-2004-0594?

Priority 53/100. EPSS top 1%: very likely to be exploited; Public exploit reference; On your watchlist

Software pages

PHP vulnerabilities · Debian vulnerabilities

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References

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