NVD / CVE Program· CNA GitHub_M

CVE-2023-27577: Path Traversal Vulnerability in `LESS` Parser allows reading of sensitive server files in flarum

MediumCVSS 4.9 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 19/100)

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: 0.85% (FIRST EPSS); higher than 58.6% of all records.
Anyone who can reach it over the internet can trigger it. Administrator privileges are required. No user action is required. No special conditions are required; it is repeatable.
Fixed version: flarum/core (Packagist) 1.7.0.

Low priority for now. Upgrade to flarum/core (Packagist) 1.7.0 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 a forum software package for building communities. In versions prior to 1.7.0 an admin account which has already been compromised by an attacker may use a vulnerability in the `LESS` parser which can be exploited to read sensitive files on the server through the use of path traversal techniques. An attacker can achieve this by providing an absolute path to a sensitive file in the custom `LESS` setting, which the `LESS` parser will then read. For example, an attacker could use the following code to read the contents of the `/etc/passwd` file on a linux machine. The scope of what files are vulnerable will depend on the permissions given to the running flarum process. The vulnerability has been addressed in version `1.7`. Users should upgrade to this version to mitigate the vulnerability. Users unable to upgrade may mitigate the vulnerability by ensuring that their admin accounts are secured with strong passwords and follow other best practices for account security. Additionally, users can limit the exposure of sensitive files on the server by implementing appropriate file permissions and access controls at the operating system level.

Path traversal

GHSA-vhm8-wwrf-3gcw

Published: Mar 10, 2023
Updated: Jun 17, 2026
EPSS: 0.8% · 58th percentile
CWE: CWE-22

Report tools

JSON

Action score

Monitor

Low priority for now.

CVSS: 19 / 40 · 4.9 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.8%

CISA SSVC decision

Exploitation: none
Automatable: no
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: 4.9
CNA · GitHub_M: 6.6; 1.7 point gap

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

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.

Is your version affected? Check it

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.

We use this product, ask for help

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.

Vendor	Product	CPE
flarum	flarum	cpe:2.3:a:flarum:flarum

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
- < 1.7.0affected

Affected versions

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

flarum flarumbefore 1.7.0

Package-level exposure

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

Ecosystem	Package	Affected range	Fix
Packagist	flarum/core	before 1.7.0	1.7.0

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-2023-22488Jan 12, 2023 · Missing authorization in Flarum
21Monitor
← EarlierCVE-2023-22489Jan 13, 2023 · Flarum is missing authorization in discussion replies
14Monitor
Later →CVE-2023-40033Aug 16, 2023 · Server-Side Request Forgery via Avatar upload in flarum
28Monitor

Remediation

Which version to upgrade to

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

Product / package	Fixed version	Source
Packagist:flarum/core	1.7.0	Package 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.

flarum/frameworkcommit 1761660

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.
Administrator privileges are required.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality: high · data can be read
Integrity: none
Availability: none

Attack vector: Network
Attack complexity: Low
Privileges required: High
User interaction: None
Scope: Unchanged
Confidentiality impact: High
Integrity impact: None
Availability impact: None

Weakness class (CWE)

CWE-22 · Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

CVSS vector

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

nvd-primary

Root cause

A user-supplied file name is joined with the allowed directory, but the result is never checked to confirm it is still inside that directory.

The bug in code

The whole CWE-22 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1const file = path.join(ROOT, req.query.name);
2res.sendFile(file);

Fixed

1const file = path.resolve(ROOT, req.query.name);
2if (!file.startsWith(ROOT + path.sep)) {
3  return res.sendStatus(400);
4}
5res.sendFile(file);

Attack context

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

Attack patterns (CAPEC)

ATT&CK techniques

—

Change log (1)

Fix✗ → ✓Sep 28, 2026, 10:47 PM UTC

For records you follow, these changes also arrive as notifications. →

References

github.com/flarum/framework/commit/1761660c98ea5a3e9665fb8e6041d1f2ee62a444

Show all references (1 more)

github.com/flarum/framework/security/advisories/GHSA-vhm8-wwrf-3gcw

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

All records