# CVE-2023-26556: IO FinNet tss-lib vulnerable to timing attack from non-constant time scalar multiplication

> Attackers can recover secret keys via timing side-channel attacks in tss-lib due to non-constant-time scalar multiplication.

- **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 21 Apr 2023
- **Updated:** 5 Feb 2025
- **Also known as:** GHSA-3w84-4mjc-rjw7, GO-2023-1732

## What is CVE-2023-26556?

CVE-2023-26556 is a critical vulnerability in n/a, published on 21 Apr 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

io.finnet tss-lib before 2.0.0 can leak a secret key via a timing side-channel attack because it relies on the scalar-multiplication implementation in Go crypto/elliptic, which is not constant time (there is an if statement in a loop). One leak is in ecdsa/keygen/round_2.go. (bnb-chain/tss-lib and thorchain/tss are also affected.)

Weakness: CWE-203 (Observable Discrepancy)

## Which versions are affected by CVE-2023-26556?

6 open source packages ship an affected version, including github.com/binance-chain/tss-lib and github.com/bnb-chain/tss-lib. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/binance-chain/tss-lib` | Go | All versions | None |
| `github.com/binance-chain/tss-lib` | Go | All versions | 2.0.0 |
| `github.com/binance-chain/tss-lib` | Go | All versions | 2.0.0 |
| `github.com/bnb-chain/tss-lib` | Go | All versions | 1.3.6-0.20230324145555-bb6fb30bd3eb |
| `github.com/bnb-chain/tss-lib` | Go | All versions | 2.0.0 |
| `github.com/bnb-chain/tss-lib` | Go | All versions | 2.0.0 |

Products: Iofinnet Tss-Lib.

## How do I fix CVE-2023-26556?

Upgrade github.com/binance-chain/tss-lib to 2.0.0 or later.

## Is CVE-2023-26556 being exploited?

There is no known exploitation of CVE-2023-26556 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2023-26557](https://insights.sbomify.com/CVE-2023-26557/): IO FinNet tss-lib vulnerable to timing attack from non-constant time scalar arithmetic (high 7.5)
- [CVE-2022-47930](https://insights.sbomify.com/CVE-2022-47930/): IO FinNet tss-lib vulnerable to replay attacks involving proofs (medium 6.8)
- [CVE-2022-47931](https://insights.sbomify.com/CVE-2022-47931/): Collision of hash values in github.com/bnb-chain/tss-lib (medium 6.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-26556 and fix it if it is affected.

What it is: CVE-2023-26556 is a critical vulnerability in n/a, published on 21 Apr 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2023-26556 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/binance-chain/tss-lib (Go): affected all versions; no fix listed
- github.com/binance-chain/tss-lib (Go): affected all versions; fixed in 2.0.0
- github.com/binance-chain/tss-lib (Go): affected all versions; fixed in 2.0.0
- github.com/bnb-chain/tss-lib (Go): affected all versions; fixed in 1.3.6-0.20230324145555-bb6fb30bd3eb
- github.com/bnb-chain/tss-lib (Go): affected all versions; fixed in 2.0.0
- github.com/bnb-chain/tss-lib (Go): affected all versions; fixed in 2.0.0

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-2023-26556/ (Markdown: https://insights.sbomify.com/CVE-2023-26556/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-26556
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-26556
- OSV: https://osv.dev/vulnerability/CVE-2023-26556

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-26556/
Summaries are generated and may contain mistakes; the official description above is the record.