How severe is CVE-2020-15148?

CVE-2020-15148 has a CVSS score of 10/10, rated CRITICAL. Immediate patching is strongly recommended.

Which packages are affected by CVE-2020-15148?

CVE-2020-15148 affects the following packages: yiisoft/yii2 (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2020-15148?

Update yiisoft/yii2 to 2.0.38 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-15148 is resolved across your whole dependency graph.

How do I detect CVE-2020-15148 in my Packagist dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for yiisoft/yii2, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2020-15148 if there is no patch (or I can't update yet)?

Do not deserialise data from untrusted sources: where the format allows it, restrict deserialisation to an explicit allowlist of expected types, and prefer a data-only format (JSON, Protobuf) over one that can reconstruct arbitrary objects until you can upgrade.

Is CVE-2020-15148 actively exploited in the wild?

Yes. There are 4 known exploit references for CVE-2020-15148, including 2 in-the-wild exploitations observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2020-15148?

CVE-2020-15148 has an EPSS (Exploit Prediction Scoring System) score of 77.5%, placing it in the 100th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. A score above 50% indicates significantly elevated exploitation risk — immediate patching is strongly recommended.

What type of vulnerability is CVE-2020-15148?

CVE-2020-15148 is classified as Deserialization of Untrusted Data (CWE-502). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

Is there exploit tooling available for CVE-2020-15148?

A Nuclei detection template exists for CVE-2020-15148, meaning automated scanners can fingerprint it. Public exploit tooling significantly increases real-world risk — prioritize patching and ensure detection coverage. Exploit tooling should only ever be used in isolated, authorized testing environments.

When was CVE-2020-15148 published, and has it been updated?

CVE-2020-15148 was published on September 15, 2020 and was last updated on August 7, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐘

🐘 Packagist

Not in CISA KEV

CRITICAL severity

CVE-2020-15148 — yii2

CRITICALFix: yiisoft/yii2@9abccb9

CVE-2020-15148 is a critical-severity (CVSS 10) Deserialization of Untrusted Data vulnerability in yiisoft/yii2. 4 public exploit references exist, so weaponization risk is real. A fix is available for yiisoft/yii2 — see the affected versions and patch details below.

Unsafe deserialization in Yii 2

Also known asGHSA-699q-wcff-g9mj

Published

Sep 15, 2020

Updated

Aug 7, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

4 known

Exploitation data as of Oct 11, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

77.5%probability of exploitation in next 30 days

Very High Risk-1.22%

Lower risk than most CVEs100th percentile — riskier than 100% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2020-15148 by exploitation likelihood (EPSS) against impact (CVSS). In the shaded patch-first corner (EPSS 50%+, CVSS 7.0+).

Where this sits among everything scored

Of 385,738 CVEs with a current EPSS score, this one falls in the 50–90% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected

🐘yiisoft/yii2

Real-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

Impact

Remote code execution in case application calls unserialize() on user input containing specially crafted string.

Patches

2.0.38

Workarounds

Add the following to BatchQueryResult.php:

public function __sleep()
{
    throw new \BadMethodCallException('Cannot serialize '.__CLASS__);
}

public function __wakeup()
{
    throw new \BadMethodCallException('Cannot unserialize '.__CLASS__);
}

For more information

If you have any questions or comments about this advisory, contact us through security form.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`yiisoft/yii2`	all versions	2.0.38`composer require yiisoft/yii2:^2.0.38`

Affected Products

1 product · 1 configurations

Application

yiiyiiframework

< 2.0.38

range

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

Yii 2 (yiisoft/yii2) before version 2.0.38 is vulnerable to remote code …

github.comGithubSep 2020

Yii 2 (yiisoft/yii2) before version 2.0.38 is vulnerable to remote code …

github.comGithubOct 2020

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for yiisoft/yii2, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update yiisoft/yii2 to 2.0.38 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-15148 is resolved across your whole dependency graph.
Workarounds
Do not deserialise data from untrusted sources: where the format allows it, restrict deserialisation to an explicit allowlist of expected types, and prefer a data-only format (JSON, Protobuf) over one that can reconstruct arbitrary objects until you can upgrade.

How to detect CVE-2020-15148

A community-maintained Nuclei template exists for this CVE. You can scan for it directly:

nuclei -id cve-2020-15148 -u https://target

Template: Yii 2 < 2.0.38 - Remote Code Execution
Severity: critical
Impact: Successful exploitation of this vulnerability could allow an attacker to execute arbitrary code on the affected system.
Remediation: Upgrade to version 2.0.38 or later. A possible workaround without upgrading is available in the linked advisory.

Template by ProjectDiscovery nuclei-templates (pikpikcu), MIT licensed. View the full template. Scan only systems you are authorised to test.

Frequently Asked Questions

### Impact Remote code execution in case application calls `unserialize()` on user input containing specially crafted string. ### Patches 2.0.38 ### Workarounds Add the following to BatchQueryResult.php: ```php public function __sleep() { throw new \BadMethodCallException('Cannot serialize '.__CLASS__); } public function __wakeup() { throw new \BadMethodCallException('Cannot unserialize '.__CLASS__); } ``` ### For more information If you have any questions or comments about this advisory, [contact us through security form](https://www.yiiframework.com/security).