CVE-2025-27591 is a medium-severity (CVSS 6.8) CWE-732 vulnerability in below. 7 public exploit references exist, so weaponization risk is real. A fix is available for below — see the affected versions and patch details below.
Below has Incorrect Permission Assignment for Critical Resource
Exploitation Status
No confirmed exploitation observed yet
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2025-27591.
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
CVE-2025-27591 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 378,156 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
belowReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.
Description
Impact
A privilege escalation vulnerability existed in the Below service prior to v0.9.0 due to the creation of a world-writable directory at /var/log/below. This could have allowed local unprivileged users to escalate to root privileges through symlink attacks that manipulate files such as /etc/shadow.
Patches
https://github.com/facebookincubator/below/commit/10e73a21d67baa2cd613ee92ce999cda145e1a83
This is included in version 0.9.0
Workarounds
Change the permission on /var/log/below manually
References
https://www.facebook.com/security/advisories/cve-2025-27591 https://www.cve.org/CVERecord?id=CVE-2025-27591
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | below | all versions | 0.9.0cargo update -p below --precise 0.9.0 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
BridgerAlderson/CVE-2025-27591-PoC
CVE-2025-27591 is a privilege escalation vulnerability that affected the
0x00Jeff/CVE-2025-27591
self cleaning CVE-2025-27591 Poc that grants a root reverse shell instea
obamalaolu/CVE-2025-27591
CVE-2025-27591
dollarboysushil/Linux-Privilege-Escalation-CVE-2025-27591
CVE-2025-27591 is a known privilege escalation vulnerability in the Belo
incommatose/CVE-2025-27591-PoC
A Proof of Concept for CVE-2025-27591, a local privilege escalation in B
rvzsec/CVE-2025-27591
Below v0.8.1 - Local Privilege Escalation (CVE-2025-27591) - PoC Exploit
Cythonic1/CVE-2025-27591
a C exploit for CVE-2025-27591, which allow an attacker to escalate priv
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for below, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update below to 0.9.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-27591 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 CVE-2025-27591 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2025-27591. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2025-27591 in your dependencies?
O3 Security finds CVE-2025-27591 across crates.io dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.