CVE-2026-25726 — v4
HIGHCVE-2026-25726 is a high-severity (CVSS 8.1) CWE-338 vulnerability in github.com/cloudreve/Cloudreve/v4. A fix is available for github.com/cloudreve/Cloudreve/v4 — see the affected versions and patch details below.
Cloudreve is vulnerable to Account Takeover via Weak Cryptographic Token Generation (Insecure PRNG Seeding)
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-2026-25726.
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-2026-25726 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
github.com/cloudreve/Cloudreve/v4Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Impact
This vulnerability affects Cloudreve instances that were first deployed/initialized with versions prior to V4.10.0.
The application uses the weak pseudo-random number generator math/rand seeded with time.Now().UnixNano() to generate critical security secrets, including the secret_key, and hash_id_salt. These secrets are generated upon first startup and persisted in the database.
An attacker can exploit this by obtaining the administrator's account creation time (via public API endpoints) to narrow the search window for the PRNG seed, and use known hashid to validate the seed. By brute-forcing the seed (demonstrated to take <3 hours on general consumer PC), an attacker can predict the secret_key. This allows them to forge valid JSON Web Tokens (JWTs) for any user, including administrators, leading to full account takeover and privilege escalation.
Note: Servers running V4.10.0+ are still vulnerable if they were originally installed using an older version, as the weak secrets persist in the configuration.
Patches
The issue has been addressed in version 4.13.0. This patch introduces a migration mechanism that automatically:
- Invalidate the existing
secret_key. - Regenerate a new, cryptographically secure
secret_keyusing crypto/rand.
Users should upgrade to 4.13.0 immediately.
Workarounds
If an immediate upgrade is not possible, administrators must manually rotate the critical secrets in the configuration file to invalidate potential exploits:
- Stop the Cloudreve service.
- In Cloudreve database, locate
secret_keysetting. - Replace the value with a long, random string (e.g., generated via
openssl rand -base64 64). - Restart the Cloudreve service.
Note: This will log out all currently active users.
Resources
- Vulnerable Code (Seeding): https://github.com/cloudreve/cloudreve/blob/87d48ac4a7acbc68064c2b9cb23793ac97f4392d/pkg/util/common.go#L21C1-L23C2
- Vulnerable Code (Usage): https://github.com/cloudreve/cloudreve/blob/87d48ac4a7acbc68064c2b9cb23793ac97f4392d/inventory/setting.go#L591
- Go Documentation (math/rand)
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/cloudreve/Cloudreve/v4 | all versions | 4.0.0-20260205113604-ec9fdd33bc54go get github.com/cloudreve/Cloudreve/v4@v4.0.0-20260205113604-ec9fdd33bc54 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/cloudreve/Cloudreve/v4, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/cloudreve/Cloudreve/v4 to 4.0.0-20260205113604-ec9fdd33bc54 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-25726 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-2026-25726 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-25726. 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-2026-25726 in your dependencies?
O3 Security finds CVE-2026-25726 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.