# RUSTSEC-2026-0240: Ed25519 identity public keys permit universal signature forgery


- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 9 Aug 2026
- **Also known as:** GHSA-7j32-2mpw-c784

## What is RUSTSEC-2026-0240?

RUSTSEC-2026-0240 is a vulnerability in dcrypt-sign, published on 9 Aug 2026. 

### Official description

All published versions of `dcrypt-sign` before 2.0.0 accepted the Edwards
identity as an Ed25519 public key. A signature with `R = B` and `S = 1` then
verified for every message because the challenge term multiplied the identity.
The implementation also admitted other noncanonical or small-order inputs.
Consumers that accepted externally supplied dcrypt Ed25519 keys may therefore
have accepted forged authorizations.

Version 2.0.0 replaces the custom arithmetic with `ed25519-dalek`, uses strict
verification, and rejects noncanonical, small-order, and non-torsion-free public
keys and `R` values, as well as noncanonical `S >= L`. No wrapper around the
affected verifier is recommended as a complete workaround. Upgrade to 2.0.0 or
later, audit registered keys and trust stores, and review historical actions
authorized with externally supplied keys.

## Which versions are affected by RUSTSEC-2026-0240?

1 open source package ship an affected version, including dcrypt-sign.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `dcrypt-sign` | crates.io | From 0.0.0-0 | 2.0.0 |

## How do I fix RUSTSEC-2026-0240?

Upgrade dcrypt-sign to 2.0.0 or later.

## Is RUSTSEC-2026-0240 being exploited?

There is no known exploitation of RUSTSEC-2026-0240 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for RUSTSEC-2026-0240 and fix it if it is affected.

What it is: RUSTSEC-2026-0240 is a vulnerability in dcrypt-sign, published on 9 Aug 2026. 
Exploitation: There is no known exploitation of RUSTSEC-2026-0240 in the wild and no public exploit code.

Affected packages and fixed versions:
- dcrypt-sign (crates.io): affected from 0.0.0-0; 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/RUSTSEC-2026-0240/ (Markdown: https://insights.sbomify.com/RUSTSEC-2026-0240/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/RUSTSEC-2026-0240

---
From sbomify Insights: https://insights.sbomify.com/RUSTSEC-2026-0240/
Summaries are generated and may contain mistakes; the official description above is the record.