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CVE-2020-8131· NVD / CVE Program· CNA hackerone

Arbitrary filesystem write vulnerability in Yarn before 1.22.0 allows attackers to write to any path on the filesystem and potentially lead

Arbitrary filesystem write vulnerability in Yarn before 1.22.0 allows attackers to write to any path on the filesystem and potentially lead to arbitrary code execution by forcing the user to install a malicious package.

HighCVSS 7.5 · v3.1—No exploit Fix available
Published
Feb 24, 2020
Updated
Jun 16, 2026
EPSS
5.2% · 92th percentile
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Report tools

JSON

Action score

32

Monitor

Low priority for now.

CVSS
30 / 40 · 7.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
2 / 30 · 5.2%

Affected systems

VendorProduct
yarnpkgyarn

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • yarnpkg yarnup to 1.21.1 inclusive

Versions reported by the vendor

Affected version ranges reported by the assigning authority (hackerone). Independent of NVD's CPE analysis and usually ahead of it.

  • n/a yarn

    • Fixed Version: 1.22.0affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12node-yarnpkgbefore 1.22.4-21.22.4-2
npmyarnbefore 1.22.01.22.0

Same product

yarnpkg: all records

Other highest-scoring records for the same primary product.

  • CVE-2019-5448Yarn before 1.17.3 is vulnerable to Missing Encryption of Sensitive Data due to HTTP URLs in lockfile causing unencrypted authentication dat
    32Monitor
  • CVE-2021-4435Yarn: untrusted search path
    31Monitor
  • CVE-2019-10773In Yarn before 1.21.1, the package install functionality can be abused to generate arbitrary symlinks on the host filesystem by using specia
    31Monitor
  • CVE-2019-15608The package integrity validation in yarn < 1.19.0 contains a TOCTOU vulnerability where the hash is computed before writing a package to cac
    24Monitor
  • CVE-2025-8262yarnpkg Yarn hosted-git-resolver.js explodeHostedGitFragment redos
    21Monitor
  • CVE-2025-9308yarnpkg Yarn request-manager.js setOptions redos
    19Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
debian:node-yarnpkg1.22.4-2 · Debian:12Package registry (OSV)
npm:yarn1.22.0Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • A user must open a link or visit a page.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-22 · Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

CVSS vector

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

nvd-primary

Root cause

A user-supplied file name is joined with the allowed directory, but the result is never checked to confirm it is still inside that directory.

The bug in code

The whole CWE-22 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

ts
const file = path.join(ROOT, req.query.name);res.sendFile(file);

Fixed

ts
const file = path.resolve(ROOT, req.query.name);if (!file.startsWith(ROOT + path.sep)) {  return res.sendStatus(400);}res.sendFile(file);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Noroxi analysis

No Noroxi analysis for this record yet

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Change log

  1. Fix✗ → ✓

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References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records