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Not in CISA KEV
HIGH severity

CVE-2026-29199 — phpbb

HIGH

CVE-2026-29199 is a high-severity (CVSS 8.1) CWE-640 vulnerability in phpbb/phpbb. A fix is available for phpbb/phpbb — see the affected versions and patch details below.

phpBB has Password Reset Link Poisoning via Host Header injection

Also known asGHSA-7gm6-w7mx-58cr
Published
Updated
Affected
2 pkgs
Patched
2 / 2
Exploits
None indexed
Exploitation data as of Nov 7, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • A successful exploit gives an attacker total control of the affected component, not partial access.
  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-29199.

EPSS Exploitation Probability

via FIRST.org ↗
0.2%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs16th percentile — riskier than 16% of all scored CVEsHighest risk
0.00%0.31%0.63%0.94%0.0%0.2%Jun 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

2 pkgs affected
🐘phpbb/phpbb🐘phpbb/phpbb

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

Description

phpBB before 3.3.16 is vulnerable to Host Header Injection that can lead to password rest link poisoning. When force_server_vars is disabled, the servers hostname may be extracted from the HTTP Host header which is used to generate the password reset link URL. An attacker who can manipulate the Host header (e.g. through misconfigured host setup or missing header validation by the webserver) can cause password reset emails to contain a link pointing to an attacker-controlled domain, potentially leading to account takeover.

Affected Packages

2 total 2 fixed
EcosystemPackageVulnerable rangeFix
🐘Packagistphpbb/phpbb≥ 3.0.0&&< 3.3.163.3.16composer require phpbb/phpbb:^3.3.16
🐘Packagistphpbb/phpbb≥ 4.0.0-a1&&< 4.0.0-a24.0.0-a2composer require phpbb/phpbb:^4.0.0-a2

Affected Products

1 product · 1 configurations
Application
phpbbphpbb
< 3.3.16
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for phpbb/phpbb, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update phpbb/phpbb to 3.3.16 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-29199 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

phpBB before 3.3.16 is vulnerable to Host Header Injection that can lead to password rest link poisoning. When force_server_vars is disabled, the servers hostname may be extracted from the HTTP Host header which is used to generate the password reset link URL. An attacker who can manipulate the Host header (e.g. through misconfigured host setup or missing header validation by the webserver) can cause password reset emails to contain a link pointing to an attacker-controlled domain, potentially leading to account takeover.
O3 Security · Impact-Aware SCA

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CVE-2026-29199: phpbb — Fixed in 3.3.16