# CVE-2026-66901: Google::Auth versions before 0.09 for Perl allow server side request forgery and credential exfiltration via unvalidated URLs taken from the credentials JSON.


- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 4 Aug 2026
- **Updated:** 5 Aug 2026
- **Also known as:** GHSA-xxpm-5c34-x4c3

## What is CVE-2026-66901?

CVE-2026-66901 is a high-severity vulnerability in CJCOLLIER Google::Auth, published on 4 Aug 2026. 

### Official description

Google::Auth versions before 0.09 for Perl allow server side request forgery and credential exfiltration via unvalidated URLs taken from the credentials JSON.

The URLs the library requests are read from the credentials JSON, and their hosts were not checked against the universe domain before the request. For an external_account configuration, retrieve_subject_token fetched credential_source.url with headers from the same JSON, and fetch_access_token posted the subject token to token_url, then sent the STS access token it received to service_account_impersonation_url in an Authorization: Bearer header. The authorized_user, impersonated_service_account and service_account configurations posted the client secret and refresh token, the source access token, and a signed JWT assertion to their own JSON-supplied token_uri or impersonation URL.

Any caller that builds credentials from a configuration it does not fully control issues those requests from the application's network position, reaching hosts the configuration names, including internal services and link-local metadata endpoints, and hands them the credentials each request carries. The service_account assertion is bound to aud, so it is not replayable against Google.

Version 0.06 added a _validate_url host check to the external_account class, keyed on a universe_domain read from the same credentials JSON. Version 0.07 gated a JSON-supplied universe domain behind GOOGLE_EXTERNAL_ACCOUNT_ALLOW_CUSTOM_UNIVERSES=1, deriving the pin flag from arguments that an earlier BUILDARGS pass had already merged on the make_creds path. Version 0.08 passed the pin decision through as an explicit constructor argument and moved _validate_url to Google::Auth::Credentials, adding the call to UserRefreshCredentials and ImpersonatedServiceAccountCredentials, and 0.09 added it to ServiceAccountCredentials.

Weakness: CWE-918 (Server-Side Request Forgery), CWE-201 (Insertion of Sensitive Information Into Sent Data)

## Which versions are affected by CVE-2026-66901?


## How do I fix CVE-2026-66901?

No fix has been published for CVE-2026-66901 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-66901 being exploited?

There is no known exploitation of CVE-2026-66901 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-66901 and fix it if it is affected.

What it is: CVE-2026-66901 is a high-severity vulnerability in CJCOLLIER Google::Auth, published on 4 Aug 2026. 
Exploitation: There is no known exploitation of CVE-2026-66901 in the wild and no public exploit code.

Affected product: CJCOLLIER Google::Auth. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-66901/ (Markdown: https://insights.sbomify.com/CVE-2026-66901/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-66901
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-66901
- OSV: https://osv.dev/vulnerability/CVE-2026-66901

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-66901/
Summaries are generated and may contain mistakes; the official description above is the record.