How severe is CVE-2020-26282?

CVE-2020-26282 has a CVSS score of 10/10, rated CRITICAL. Immediate patching is strongly recommended.

Which packages are affected by CVE-2020-26282?

CVE-2020-26282 affects the following packages: com.browserup:browserup-proxy (Maven). Ecosystems affected: Maven.

How do I fix CVE-2020-26282?

Update com.browserup:browserup-proxy to 2.1.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-26282 is resolved across your whole dependency graph.

How do I detect CVE-2020-26282 in my Maven dependencies?

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

How do I mitigate CVE-2020-26282 if there is no patch (or I can't update yet)?

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.

Is CVE-2020-26282 actively exploited in the wild?

Yes. There are 1 known exploit references for CVE-2020-26282, including 1 in-the-wild exploitation 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-2020-26282?

CVE-2020-26282 has an EPSS (Exploit Prediction Scoring System) score of 4.8%, placing it in the 92th 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. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2020-26282?

CVE-2020-26282 is classified as CWE-74 (CWE-74). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2020-26282 published, and has it been updated?

CVE-2020-26282 was published on December 24, 2020 and was last updated on July 9, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕

☕ Maven

Not in CISA KEV

CRITICAL severity

CVE-2020-26282 — browserup-proxy

CRITICALFix: browserup/browserup-proxy@4b38e7a

CVE-2020-26282 is a critical-severity (CVSS 10) CWE-74 vulnerability in com.browserup:browserup-proxy. 1 public exploit reference exists, so weaponization risk is real. A fix is available for com.browserup:browserup-proxy — see the affected versions and patch details below.

Server-Side Template Injection

Also known asGHSA-wmfg-55f9-j8hq

Published

Dec 24, 2020

Updated

Jul 9, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

1 known

Exploitation data as of Oct 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

4.8%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs92th percentile — riskier than 92% of all scored CVEsHighest risk

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

How urgent is this, really

CVE-2020-26282 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected

☕com.browserup:browserup-proxy

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

Impact

A Server-Side Template Injection was identified in BrowserUp Proxy enabling attackers to inject arbitrary Java EL expressions, leading to unauthenticated Remote Code Execution (RCE) vulnerability. This has been assigned CVE-2020-26282.

Patches

Effective Immediately, all users should upgrade to version 2.1.2 or higher.

Workarounds

None.

References

https://securitylab.github.com/research/bean-validation-RCE

For more information

If you have any questions or comments about this advisory:

Open an issue in the BrowserUp Proxy repo
Contact us via the BrowserUp website or email us at [email protected]

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`com.browserup:browserup-proxy`	all versions	2.1.2`com.browserup:browserup-proxy:2.1.2`

Affected Products

1 product · 1 configurations

Application

browserup proxybrowserup

< 2.1.2

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.

BrowserUp Proxy allows you to manipulate HTTP requests and responses, ca…

securitylab.github.comNVDDec 2020

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for com.browserup:browserup-proxy, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update com.browserup:browserup-proxy to 2.1.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-26282 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.

Frequently Asked Questions

### Impact A Server-Side Template Injection was identified in BrowserUp Proxy enabling attackers to inject arbitrary Java EL expressions, leading to unauthenticated Remote Code Execution (RCE) vulnerability. This has been assigned CVE-2020-26282. ### Patches Effective Immediately, all users should upgrade to version 2.1.2 or higher. ### Workarounds None. ### References https://securitylab.github.com/research/bean-validation-RCE ### For more information If you have any questions or comments about this advisory: * Open an issue in [the BrowserUp Proxy repo](http://github.com/browserup/brow