GHSA-4486-gxhx-5mg7 — psy/psysh
MEDIUMGHSA-4486-gxhx-5mg7 is a medium-severity (CVSS 6.7) CWE-427 vulnerability in psy/psysh. A fix is available for psy/psysh — see the affected versions and patch details below.
PsySH has Local Privilege Escalation via CWD .psysh.php auto-load
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for GHSA-4486-gxhx-5mg7.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-4486-gxhx-5mg7 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 376,715 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
psy/psysh🐘psy/psyshReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
Summary
PsySH automatically loads and executes a .psysh.php file from the Current Working Directory (CWD) on startup. If an attacker can write to a directory that a victim later uses as their CWD when launching PsySH, the attacker can trigger arbitrary code execution in the victim's context. When the victim runs PsySH with elevated privileges (e.g., root), this results in local privilege escalation.
Details
PsySH supports per-directory configuration via a .psysh.php file located in the process CWD. This file is executed implicitly when PsySH starts, without requiring explicit opt-in and without validating that the file and directory are safe (e.g., owned by the current user and not group/world-writable).
This enables a CWD poisoning scenario: a low-privileged user can plant a malicious .psysh.php in any directory they can write to, then wait for a higher-privileged user to start PsySH while their shell is in that directory.
PoC
- As a low-privileged user, create a malicious
.psysh.phpin an attacker-writable directory (example:/tmp):
bob@localhost:/tmp$ echo "<?php system('id > poc.txt'); ?>" > .psysh.php
bob@localhost:/tmp# ls -lah .psysh.php
-rw-r--r-- 1 bob bob 33 Jan 28 11:17 .psysh.php
- As the victim user, start PsySH with CWD set to that directory and exit:
root@localhost:/tmp# cd /tmp
root@localhost:/tmp# ./psysh
Psy Shell v0.12.18 (PHP 8.1.2-1ubuntu2.23 — cli) by Justin Hileman
New PHP manual is available (latest: 3.0.1). Update with `doc --update-manual`
> exit
INFO Goodbye.
- Verify code execution triggered in the victim context:
bob@localhost:/tmp$ ls -lah poc.txt
-rw-r--r-- 1 root root 39 Jan 28 11:19 poc.txt
bob@localhost:/tmp$ cat poc.txt
uid=0(root) gid=0(root) groups=0(root)
Impact
This is a CWD configuration poisoning issue leading to arbitrary code execution in the victim user’s context. If a privileged user (e.g., root, a CI runner, or an ops/debug account) launches PsySH with CWD set to an attacker-writable directory containing a malicious .psysh.php, the attacker can execute commands with that privileged user’s permissions, resulting in local privilege escalation.
Downstream consumers that embed PsySH inherit this risk. For example, Laravel Tinker (php artisan tinker) uses PsySH. If a privileged user runs Tinker while their shell is in an attacker-writable directory, the .psysh.php auto-load behavior can be abused in the same way to execute attacker-controlled code under the victim’s privileges.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | psy/psysh | ≥ 0.12.0&&< 0.12.19 | 0.12.19composer require psy/psysh:^0.12.19 |
| 🐘Packagist | psy/psysh | all versions | 0.11.23composer require psy/psysh:^0.11.23 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for psy/psysh, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update psy/psysh to 0.12.19 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-4486-gxhx-5mg7 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-4486-gxhx-5mg7 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-4486-gxhx-5mg7. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-4486-gxhx-5mg7 in your dependencies?
O3 Security finds GHSA-4486-gxhx-5mg7 across Packagist dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.