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NVD / CVE Program· CNA GitHub_M

CVE-2025-27794: Flarum Vulnerable to Session Hijacking via Authoritative Subdomain Cookie Overwrite

MediumCVSS 6.8 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 27/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.50% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. A user must open a link or visit a page. Special conditions such as timing or configuration are required.
  • Fixed version: flarum/core (Packagist) 1.8.10; flarum/framework (Packagist) 1.8.10.

Low priority for now. Upgrade to flarum/core (Packagist) 1.8.10; flarum/framework (Packagist) 1.8.10 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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 are that the attacker must control any subdomain under the parent domain (e.g., `evil.host.com` or `x.y.host.com`), and the parent domain must not be on the Public Suffix List. Due to non-existent session token rotation after authenticating we can theoretically reproduce the vulnerability by using browser dev tools, but due to the browser's security measures this does not seem to be exploitable as described. Version 1.8.10 contains a patch for the issue.

Published
Mar 12, 2025
Updated
Jun 17, 2026
EPSS
0.5% · 43th percentile

Report tools

JSON

Action score

27

Monitor

Low priority for now.

CVSS
27 / 40 · 6.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.5%

CISA SSVC decision

Exploitation
proof of concept
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
6.8
CNA · GitHub_M
6.8
agree

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2025-27794

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
flarumflarum

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

  • flarum framework

    • < 1.8.10affected

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • flarum flarumbefore 1.8.0

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Packagistflarum/corebefore 1.8.101.8.10
Packagistflarum/frameworkbefore 1.8.101.8.10

Same product

flarum: all records

Other highest-scoring records for the same primary product.

  • CVE-2021-32671XSS vulnerability with translator
    52Plan
  • CVE-2019-13183Flarum before 0.1.0-beta.9 allows CSRF against all POST endpoints, as demonstrated by changing admin settings.
    35Monitor
  • CVE-2019-11514User/Command/ConfirmEmailHandler.php in Flarum before 0.1.0-beta.8 mishandles invalidation of user email tokens.
    30Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2023-27577Mar 10, 2023 · Path Traversal Vulnerability in `LESS` Parser allows reading of sensitive server files in flarum
    19Monitor
  • ← EarlierCVE-2023-40033Aug 16, 2023 · Server-Side Request Forgery via Avatar upload in flarum
    28Monitor
  • ← EarlierCVE-2024-21641Jan 5, 2024 · Flarum's Logout Route allows open redirects
    18Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Packagist:flarum/core1.8.10Package registry (OSV)
Packagist:flarum/framework1.8.10Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Not on record for this CVE: EPSS history · researcher credit · variant or chain candidate · public bounty program.

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • A user must open a link or visit a page.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
none
Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
None

Weakness class (CWE)

CWE-74 · Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

References

Show all references (2 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records