CVE-2025-27794: Flarum is open-source forum software

Q: How do I fix CVE-2025-27794?

flarum: upgrade to 1.8.0. Exact commands for each OS are on this page.

Q: Is CVE-2025-27794 being exploited?

CVE-2025-27794 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-2025-27794 affect?

CVE-2025-27794 affects flarum. Severity is medium (CVSS 6.8). Flarum is open-source forum software. A session hijacking vulnerability exists in versions prior to 1.8.10 when an attacker-controlled authoritative subdomain under a parent domain (e.g., `subdomain.host.com`) sets cookies scoped to the par

Q: How urgent is CVE-2025-27794?

Priority 35/100. No elevated risk signals yet.

Routine

MEDIUM 6.8UPGRADE

CVE-2025-27794 is a medium-severity flaw (CVSS 6.8) affecting flarum. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Flarum is open-source forum software. A session hijacking vulnerability exists in versions prior to 1.8.10 when an attacker-controlled authoritative subdomain under a parent domain (e.g., `subdomain.host.com`) sets cookies scoped to the parent domain (`.host.com`). This allows session token replacement for applications hosted on sibling subdomains (e.g., `community.host.com`) if session tokens aren't rotated post-authentication. Key Constraints a

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	6.8 (Medium)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.5% (top 57%)
CISA exploited list	No
Weakness	CWE-74
Published	2025-03-12
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: flarum

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

Am I affected?

Timeline

2025-03-12 14:15 UTCPublished CVE record published
2026-06-17 09:04 UTCUpdated Record last modified

flarum flarum UPGRADE

Affected: < 1.8.0

Fixed in: 1.8.0

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 1.8.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade flarum

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade flarum

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

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-2025-27794?

flarum: upgrade to 1.8.0. Exact commands for each OS are on this page.

Is CVE-2025-27794 being exploited?

CVE-2025-27794 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-2025-27794 affect?

CVE-2025-27794 affects flarum. Severity is medium (CVSS 6.8). Flarum is open-source forum software. A session hijacking vulnerability exists in versions prior to 1.8.10 when an attacker-controlled authoritative subdomain under a parent domain (e.g., `subdomain.host.com`) sets cookies scoped to the par

How urgent is CVE-2025-27794?

Priority 35/100. No elevated risk signals yet.

References

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