CVE-2015-4602: The __PHP_Incomplete_Class function in ext/standard/incomplete_class.c in PHP before 5.4.40, 5.5.x before 5.5.

Q: How do I fix CVE-2015-4602?

enterprise linux: mitigate or apply the listed mitigation; php: upgrade to newer than 5.4.39; enterprise linux desktop: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2015-4602 being exploited?

CVE-2015-4602 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2015-4602 affect?

CVE-2015-4602 affects enterprise linux, php, enterprise linux desktop. Severity is critical (CVSS 9.8). The __PHP_Incomplete_Class function in ext/standard/incomplete_class.c in PHP before 5.4.40, 5.5.x before 5.5.24, and 5.6.x before 5.6.8 allows remote attackers to cause a denial of service (application crash) or possibly execute arbitrary

Q: How urgent is CVE-2015-4602?

Priority 73/100. Critical severity; EPSS top 4%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist

This week

CRITICAL 9.8REMOTEWATCHLISTMITIGATEUPGRADEMITIGATE

CVE-2015-4602 is a critical-severity flaw (CVSS 9.8) affecting enterprise linux, php, enterprise linux desktop. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The __PHP_Incomplete_Class function in ext/standard/incomplete_class.c in PHP before 5.4.40, 5.5.x before 5.5.24, and 5.6.x before 5.6.8 allows remote attackers to cause a denial of service (application crash) or possibly execute arbitrary code via an unexpected data type, related to a "type confusion" issue.

Why this priority

Critical severity
EPSS top 4%: very likely to be exploited
Public exploit reference
Remotely exploitable, no login, no user action
On your watchlist

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	10.3% (top 4%)
CISA exploited list	No
Published	2016-05-16
Last modified	2026-06-17

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

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

Am I affected?

Timeline

2016-05-16 10:59 UTCPublished CVE record published
2026-06-17 00:27 UTCUpdated Record last modified

redhat enterprise linux MITIGATE

Affected: 6.0 · 7.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 6.0

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.

php php UPGRADE

Affected: <= 5.4.39 · 5.5.0 · 5.5.1 · 5.5.2 · 5.5.3 · 5.5.4 · 5.5.5 · 5.5.6

Fixed in: newer than 5.4.39

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to newer than 5.4.39 (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.

redhat enterprise linux desktop MITIGATE

Affected: 7.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.0

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.

redhat enterprise linux hpc node MITIGATE

Affected: 7.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.0

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.

redhat enterprise linux hpc node eus MITIGATE

Affected: 7.1

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.1

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.

redhat enterprise linux server MITIGATE

Affected: 7.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.0

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.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.

Fedora 46 · rust-ingredients · FIXED · 0.3.3-2.fc46 · FEDORA-2026-0b3d9feffd · source

sudo dnf upgrade --advisory=FEDORA-2026-0b3d9feffd

Fedora ELN · dpkg · FIXED · 1.23.11-2.eln159 · FEDORA-2026-732e4ac21b · source

sudo dnf upgrade --advisory=FEDORA-2026-732e4ac21b

RHEL 6 · php · FIXED · php-5.3.3-46.el6_6

sudo dnf upgrade --advisory=RHSA-2015:1218 rpm -q php

RHEL 7 · php · FIXED · php-5.4.16-36.ael7b_1

sudo dnf upgrade --advisory=RHSA-2015:1135 rpm -q php

RHEL 5 · php · DEFERRED

RHEL 5 · php53 · DEFERRED

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-2015-4602?

enterprise linux: mitigate or apply the listed mitigation; php: upgrade to newer than 5.4.39; enterprise linux desktop: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2015-4602 being exploited?

CVE-2015-4602 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-2015-4602 affect?

CVE-2015-4602 affects enterprise linux, php, enterprise linux desktop. Severity is critical (CVSS 9.8). The __PHP_Incomplete_Class function in ext/standard/incomplete_class.c in PHP before 5.4.40, 5.5.x before 5.5.24, and 5.6.x before 5.6.8 allows remote attackers to cause a denial of service (application crash) or possibly execute arbitrary

How urgent is CVE-2015-4602?

Priority 73/100. Critical severity; EPSS top 4%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist

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References

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