CVE-2006-4450: usercp_avatar.php in PHPBB 2.0.20, when avatar uploading is enabled, allows remote attackers to use the server

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MEDIUM 5.1DOWNGRADE

CVE-2006-4450 is a medium-severity flaw (CVSS 5.1) affecting phpbb. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

usercp_avatar.php in PHPBB 2.0.20, when avatar uploading is enabled, allows remote attackers to use the server as a web proxy by submitting a URL to the avatarurl parameter, which is then used in an HTTP GET request.

Why this priority

EPSS top 9%: very likely to be exploited
Public exploit reference

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

Risk facts

CVSS score	5.1 (Medium)
EPSS exploit chance	4.2% (top 9%)
CISA exploited list	No
Published	2006-08-30
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

2006-08-30 01:04 UTCPublished CVE record published
2026-06-16 22:29 UTCUpdated Record last modified

phpbb group phpbb DOWNGRADE

Affected: 2.0.20

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.0.20

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 2.0.20 (Debian / Ubuntu)

apt-cache madison phpbb sudo apt install phpbb=<VERSION_BEFORE_2.0.20> sudo apt-mark hold phpbb

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

dnf --showduplicates list phpbb sudo dnf downgrade phpbb-<VERSION_BEFORE_2.0.20> 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: phpBB 2.0.20 - Unauthorized HTTP Proxy

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-2006-4450?

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

Is CVE-2006-4450 being exploited?

CVE-2006-4450 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-2006-4450 affect?

CVE-2006-4450 affects phpbb. Severity is medium (CVSS 5.1). usercp_avatar.php in PHPBB 2.0.20, when avatar uploading is enabled, allows remote attackers to use the server as a web proxy by submitting a URL to the avatarurl parameter, which is then used in an HTTP GET request.

How urgent is CVE-2006-4450?

Priority 46/100. EPSS top 9%: 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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