How severe is CVE-2021-23664?

CVE-2021-23664 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2021-23664?

CVE-2021-23664 affects the following packages: @isomorphic-git/cors-proxy (npm). Ecosystems affected: npm.

How do I fix CVE-2021-23664?

Update @isomorphic-git/cors-proxy to 2.7.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-23664 is resolved across your whole dependency graph.

How do I detect CVE-2021-23664 in my npm dependencies?

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

How do I mitigate CVE-2021-23664 if there is no patch (or I can't update yet)?

Restrict outbound requests from the affected component to an allowlist of hosts, block access to link-local and internal address ranges at the network layer, and require authentication on internal services so a forged request cannot reach them unauthenticated.

Is CVE-2021-23664 actively exploited in the wild?

Yes. There are 1 known exploit references for CVE-2021-23664, 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-2021-23664?

CVE-2021-23664 has an EPSS (Exploit Prediction Scoring System) score of 1.4%, placing it in the 71th 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-2021-23664?

CVE-2021-23664 is classified as Server-Side Request Forgery (SSRF) (CWE-918). 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.

When was CVE-2021-23664 published, and has it been updated?

CVE-2021-23664 was published on January 21, 2022 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.

📦

📦 npm

Not in CISA KEV

HIGH severity

CVE-2021-23664 — @isomorphic-git/cors-proxy

HIGHFix: isomorphic-git/cors-proxy@1b1c91e

CVE-2021-23664 is a high-severity (CVSS 7.5) Server-Side Request Forgery (SSRF) vulnerability in @isomorphic-git/cors-proxy. 1 public exploit reference exists, so weaponization risk is real. A fix is available for @isomorphic-git/cors-proxy — see the affected versions and patch details below.

Server side request forgery in @isomorphic-git/cors-proxy

Also known asGHSA-v82v-rq72-phq9SNYK-JS-ISOMORPHICGITCORSPROXY-1734788

Published

Jan 21, 2022

Updated

Jul 9, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

1 known

Exploitation data as of Sep 27, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

1.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs71th percentile — riskier than 71% of all scored CVEsHighest risk

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

How urgent is this, really

CVE-2021-23664 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

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

6other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

@isomorphic-git/cors-proxynpm

966downloads / week

Description

The package @isomorphic-git/cors-proxy before 2.7.1 are vulnerable to Server-side Request Forgery (SSRF) due to missing sanitization and validation of the redirection action in middleware.js.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`@isomorphic-git/cors-proxy`	all versions	2.7.1`npm install @isomorphic-git/cors-proxy@2.7.1`

Affected Products

1 product · 1 configurations

Application

cors-proxyisomorphic-git

< 2.7.1

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.

The package @isomorphic-git/cors-proxy before 2.7.1 are vulnerable to Se…

snyk.ioNVDJan 2022

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @isomorphic-git/cors-proxy, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @isomorphic-git/cors-proxy to 2.7.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-23664 is resolved across your whole dependency graph.
Workarounds
Restrict outbound requests from the affected component to an allowlist of hosts, block access to link-local and internal address ranges at the network layer, and require authentication on internal services so a forged request cannot reach them unauthenticated.

Frequently Asked Questions

The package @isomorphic-git/cors-proxy before 2.7.1 are vulnerable to Server-side Request Forgery (SSRF) due to missing sanitization and validation of the redirection action in middleware.js.

O3 Security · Impact-Aware SCA

Is CVE-2021-23664 in your dependencies?

Find it across npm, including transitive dependencies.

Scan my dependencies How O3 SCA works

CVSS Score

7.5/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

None

Availability

None

Raw vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

CWE Classification

CWE-918Server-Side Request Forgery (SSRF)

Weaponization

No known public exploit tooling found.

OpenSSF Scorecard

Package health score

cors-proxy

2.4/10

Maintained0/10

Code-Review1/10

Branch-Protection0/10

Assessed Sep 21, 2026

Timeline

Disclosed

Jan 21, 2022

First exploit

Jan 28, 2022

7 days after disclosure — rapid exploitation

Last updated

Jul 9, 2026

Identifiers

CVE-2021-23664

GHSA-v82v-rq72-phq9

SNYK-JS-ISOMORPHICGITCORSPROXY-1734788

References

Advisorynvd.nist.gov Fixgithub.com Fixsnyk.io Packagegithub.com

Related vulnerabilities

This CVE is high severity; 5 of 8 other CVEs with CWE-918 are rated as high or higher (top: critical).

GHSA-39wr-7q6h-cf68GHSA-jgh3-fggc-mcpmCVE-2026-85732CVE-2026-59823CVE-2026-61793CVE-2026-73247CVE-2026-61559CVE-2026-59973Browse all CWE-918

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedJul 9, 2026

CVE-2021-23664 — @isomorphic-git/cors-proxy

EPSS Exploitation Probability

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

Description

Affected Packages

Affected Products

Detection & mitigation playbook

Detect

Fix

Workarounds

Frequently Asked Questions

Is CVE-2021-23664 in your dependencies?