How severe is CVE-2021-41087?

CVE-2021-41087 has a CVSS score of 6.5/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2021-41087?

CVE-2021-41087 affects the following packages: github.com/in-toto/in-toto-golang (Go). Ecosystems affected: Go.

How do I fix CVE-2021-41087?

Update github.com/in-toto/in-toto-golang to 0.3.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-41087 is resolved across your whole dependency graph.

How do I detect CVE-2021-41087 in my Go dependencies?

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

How do I mitigate CVE-2021-41087 if there is no patch (or I can't update yet)?

Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.

Is CVE-2021-41087 actively exploited in the wild?

No public exploit code has been indexed for CVE-2021-41087 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2021-41087?

CVE-2021-41087 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 35th 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-2021-41087?

CVE-2021-41087 is classified as CWE-345 (CWE-345), Path Traversal (CWE-22). These weakness types 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-2021-41087 published, and has it been updated?

CVE-2021-41087 was published on September 21, 2021 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.

🐹

🐹 Go

Not in CISA KEV

MEDIUM severity

CVE-2021-41087 — in-toto-golang

MEDIUMFix: in-toto/in-toto-golang@f2c57d1

CVE-2021-41087 is a medium-severity (CVSS 6.5) CWE-345 vulnerability in github.com/in-toto/in-toto-golang. A fix is available for github.com/in-toto/in-toto-golang — see the affected versions and patch details below.

Improperly Implemented path matching for in-toto-golang

Also known asGHSA-vrxp-mg9f-hwf3GO-2022-0936

Published

Sep 21, 2021

Updated

Jul 9, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 12, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs35th percentile — riskier than 35% of all scored CVEsHighest risk

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

How urgent is this, really

CVE-2021-41087 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,987 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

🐹github.com/in-toto/in-toto-golang

Real-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

Authenticated attackers posing as functionaries (i.e., within a trusted set of users for a layout) are able to create attestations that may bypass DISALLOW rules in the same layout. An attacker with access to trusted private keys, may issue an attestation that contains a disallowed artifact by including path traversal semantics (e.g., foo vs dir/../foo).

Patches

The problem has been fixed in version 0.3.0.

Workarounds

Exploiting this vulnerability is dependent on the specific policy applied.

For more information

If you have any questions or comments about this advisory:

Open an issue in in-toto-golang
Email us at in-toto-public
If this is a sensitive security-relevant disclosure, please send a PGP encrypted email to [email protected] or [email protected]

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/in-toto/in-toto-golang`	all versions	0.3.0`go get github.com/in-toto/in-toto-golang@v0.3.0`

Affected Products

1 product · 1 configurations

Application

in-toto-golangin-toto

< 0.3.0

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/in-toto/in-toto-golang, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/in-toto/in-toto-golang to 0.3.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-41087 is resolved across your whole dependency graph.
Workarounds
Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.

Frequently Asked Questions

### Impact Authenticated attackers posing as functionaries (i.e., within a trusted set of users for a layout) are able to create attestations that may bypass DISALLOW rules in the same layout. An attacker with access to trusted private keys, may issue an attestation that contains a disallowed artifact by including path traversal semantics (e.g., foo vs dir/../foo). ### Patches The problem has been fixed in version 0.3.0. ### Workarounds Exploiting this vulnerability is dependent on the specific policy applied. ### For more information If you have any questions or comments about this advisor