CVE-2006-6840: Unspecified vulnerability in phpBB before 2.0.22 has unknown impact and remote attack vectors related to a "ne

This month

HIGH 10.0DOWNGRADE

CVE-2006-6840 is a high-severity flaw (CVSS 10.0) affecting phpbb. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Unspecified vulnerability in phpBB before 2.0.22 has unknown impact and remote attack vectors related to a "negative start parameter."

Why this priority

Critical severity

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

Risk facts

CVSS score	10.0 (High)
EPSS exploit chance	1.7% (top 23%)
CISA exploited list	No
Published	2006-12-31
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

2006-12-31 05:00 UTCPublished CVE record published
2026-06-16 22:33 UTCUpdated Record last modified

phpbb group phpbb DOWNGRADE

Affected: 1.2.4_rc3 · 2.0.18 · 2.0.20 · 2.0.21

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.2.4_rc3

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 1.2.4_rc3 (Debian / Ubuntu)

apt-cache madison phpbb sudo apt install phpbb=<VERSION_BEFORE_1.2.4_rc3> sudo apt-mark hold phpbb

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

dnf --showduplicates list phpbb sudo dnf downgrade phpbb-<VERSION_BEFORE_1.2.4_rc3> 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.

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-2006-6840?

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

Is CVE-2006-6840 being exploited?

CVE-2006-6840 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-2006-6840 affect?

CVE-2006-6840 affects phpbb. Severity is high (CVSS 10.0). Unspecified vulnerability in phpBB before 2.0.22 has unknown impact and remote attack vectors related to a "negative start parameter."

How urgent is CVE-2006-6840?

Priority 54/100. Critical severity

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

← Back to latest CVEs