Path Traversal Vulnerability in LESS Parser allows reading of sensitive server files

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2023-27577: 0.85% estimated exploitation activity in the next 30 days; percentile 58.25 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact If an admin account has already been compromised by an attacker, the LESS parser 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: Patches The vulnerability has been addressed in version 1.7. Users should upgrade to this version to mitigate the vulnerability. Workarounds Users can mitigate the vulnerability by ensuring that their admin accounts are secured with strong passwords and 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.

Published by the source

13 Mar 2023, 20:52 UTC

Last modified by the source

13 Mar 2023, 20:52 UTC

Source last checked

26 Oct 2026, 14:05 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-vhm8-wwrf-3gcw

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# Patch Next advisory brief: CVE-2023-27577

Advisory: Path Traversal Vulnerability in `LESS` Parser allows reading of sensitive server files
IDs: CVE-2023-27577, GHSA-vhm8-wwrf-3gcw
Record: https://patchnext.com/advisories/cve-2023-27577 (revision 1, source checked 26 Oct 2026, 14:05 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: flarum/core 1.7.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist flarum/core: affected < 1.7.0; fixed in 1.7.0

## Suggested inspection (read-only)
- Packagist flarum/core: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on flarum/core.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-vhm8-wwrf-3gcw (GitHub-reviewed advisory GHSA-vhm8-wwrf-3gcw lists affected ranges: Packagist flarum/core >=0 <1.7.0)

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