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Vulnerability details: VCID-xxse-e4ch-h3g1
Vulnerability ID VCID-xxse-e4ch-h3g1
Aliases CVE-2025-27794
GHSA-hg9j-64wp-m9px
Summary 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.
Status Published
Exploitability 0.5
Weighted Severity 6.2
Risk 3.1
Affected and Fixed Packages Package Details
Weaknesses (3)
No exploits are available.
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N Found at https://github.com/flarum/framework
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N Found at https://github.com/flarum/framework/commit/a05aaea3ee1e0a8b870935183193cd6052f1d402
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none


Vector: SSVCv2/E:P/A:N/T:P/P:M/B:A/M:M/D:T/2025-03-12T15:26:50Z/ Found at https://github.com/flarum/framework/commit/a05aaea3ee1e0a8b870935183193cd6052f1d402
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N Found at https://github.com/flarum/framework/releases/tag/v1.8.10
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none


Vector: SSVCv2/E:P/A:N/T:P/P:M/B:A/M:M/D:T/2025-03-12T15:26:50Z/ Found at https://github.com/flarum/framework/releases/tag/v1.8.10
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N Found at https://github.com/flarum/framework/security/advisories/GHSA-hg9j-64wp-m9px
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none


Vector: SSVCv2/E:P/A:N/T:P/P:M/B:A/M:M/D:T/2025-03-12T15:26:50Z/ Found at https://github.com/flarum/framework/security/advisories/GHSA-hg9j-64wp-m9px
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N Found at https://nvd.nist.gov/vuln/detail/CVE-2025-27794
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none

Exploit Prediction Scoring System (EPSS)
Percentile 0.59695
EPSS Score 0.00377
Published At June 11, 2026, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
2026-06-11T17:12:50.062457+00:00 Vulnrichment Import https://github.com/cisagov/vulnrichment/blob/develop/2025/27xxx/CVE-2025-27794.json 38.6.0