# CVE-2021-32738: Utils.readChallengeTx does not verify the server account signature

> The Stellar JavaScript SDK fails to verify server signatures in challenge transactions, allowing attackers to bypass authentication checks.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 2 Jul 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-6cgh-hjpw-q3gq

## What is CVE-2021-32738?

CVE-2021-32738 is a medium-severity authentication bypass vulnerability in js-stellar-sdk, published on 2 Jul 2021. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

js-stellar-sdk is a Javascript library for communicating with a Stellar Horizon server. The `Utils.readChallengeTx` function used in SEP-10 Stellar Web Authentication states in its function documentation that it reads and validates the challenge transaction including verifying that the `serverAccountID` has signed the transaction. In js-stellar-sdk before version 8.2.3, the function does not verify that the server has signed the transaction. Applications that also used `Utils.verifyChallengeTxThreshold` or `Utils.verifyChallengeTxSigners` to verify the signatures including the server signature on the challenge transaction are unaffected as those functions verify the server signed the transaction. Applications calling `Utils.readChallengeTx` should update to version 8.2.3, the first version with a patch for this vulnerability, to ensure that the challenge transaction is completely valid and signed by the server creating the challenge transaction.

Weakness: CWE-347 (Improper Verification of Cryptographic Signature), CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2021-32738?

2 open source packages ship an affected version, including stellar-sdk. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `stellar-sdk` | npm | All versions | 8.2.3 |
| `stellar-sdk` | npm | All versions | 8.2.3 |

Products: Stellar Js-Stellar-Sdk.

## How do I fix CVE-2021-32738?

Upgrade stellar-sdk to 8.2.3 or later.

## Is CVE-2021-32738 being exploited?

There is no known exploitation of CVE-2021-32738 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-32738 and fix it if it is affected.

What it is: CVE-2021-32738 is a medium-severity authentication bypass vulnerability in js-stellar-sdk, published on 2 Jul 2021. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-32738 in the wild and no public exploit code.

Affected packages and fixed versions:
- stellar-sdk (npm): affected all versions; fixed in 8.2.3
- stellar-sdk (npm): affected all versions; fixed in 8.2.3

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-2021-32738/ (Markdown: https://insights.sbomify.com/CVE-2021-32738/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-32738
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-32738
- OSV: https://osv.dev/vulnerability/CVE-2021-32738

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-32738/
Summaries are generated and may contain mistakes; the official description above is the record.