CVE-2004-1315: viewtopic.php in phpBB 2.x before 2.0.11 improperly URL decodes the highlight parameter when extracting words

This week

HIGH 7.5DOWNGRADE

CVE-2004-1315 is a high-severity flaw (CVSS 7.5) affecting phpbb. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

viewtopic.php in phpBB 2.x before 2.0.11 improperly URL decodes the highlight parameter when extracting words and phrases to highlight, which allows remote attackers to execute arbitrary PHP code by double-encoding the highlight value so that special characters are inserted into the result, which is then processed by PHP exec, as exploited by the Santy.A worm.

Why this priority

High severity
EPSS top 1%: very likely to be exploited
Public exploit reference

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

Risk facts

CVSS score	7.5 (High)
EPSS exploit chance	72.5% (top 1%)
CISA exploited list	No
Published	2004-11-12
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: phpbb group

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

Am I affected?

Timeline

2004-11-12 05:00 UTCPublished CVE record published
2026-06-16 22:07 UTCUpdated Record last modified

phpbb group phpbb DOWNGRADE

Affected: all versions · 1.0.0 · 1.0.1 · 1.2.0 · 1.2.1 · 1.4.0 · 1.4.1 · 1.4.2

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.0.0

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 1.0.0 (Debian / Ubuntu)

apt-cache madison phpbb sudo apt install phpbb=<VERSION_BEFORE_1.0.0> sudo apt-mark hold phpbb

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

dnf --showduplicates list phpbb sudo dnf downgrade phpbb-<VERSION_BEFORE_1.0.0> sudo dnf versionlock add phpbb

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-Nuke 7.0/8.1/8.1.35 - Wormable Remote Code Execution
Exploit-DB: phpBB - 'viewtopic.php' Arbitrary Code Execution (Metasploit)
Exploit-DB: phpBB 2.0.10 - Remote Command Execution
Exploit-DB: phpBB 2.0.x - 'viewtopic.php' PHP Script Injection
Metasploit: phpBB viewtopic.php Arbitrary Code Execution

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-2004-1315?

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

Is CVE-2004-1315 being exploited?

CVE-2004-1315 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-2004-1315 affect?

CVE-2004-1315 affects phpbb. Severity is high (CVSS 7.5). viewtopic.php in phpBB 2.x before 2.0.11 improperly URL decodes the highlight parameter when extracting words and phrases to highlight, which allows remote attackers to execute arbitrary PHP code by double-encoding the highlight value so th

How urgent is CVE-2004-1315?

Priority 56/100. High severity; EPSS top 1%: very likely to be exploited; Public exploit reference

Software pages

PHP vulnerabilities

Related CVEs

CVE-2026-29199 HIGH 8.1 UPGRADE phpBB before 3.3.16 is vulnerable to Host Header Injection that can lead to password rest link poisoning
CVE-2025-70811 MEDIUM 4.3 DOWNGRADE Cross Site Request Forgery vulnerability in Phpbb phbb3 v.3.3.15 allows a local attacker to execute arbitrary
CVE-2025-70810 HIGH 8.8 DOWNGRADE Cross Site Request Forgery vulnerability in Phpbb phbb3 v.3.3.15 allows a local attacker to execute arbitrary
CVE-2023-5917 LOW 2.4 UPGRADE A vulnerability, which was classified as problematic, has been found in phpBB up to 3.3.10
CVE-2020-8226 MEDIUM 5.8 UPGRADE A vulnerability exists in phpBB <v3.2.10 and <v3.3.1 which allowed remote image dimensions check to be used to

References

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