# CVE-2021-27293: Incorrect Regular Expression in RestSharp

> A malicious server response can cause the RestSharp client to hang indefinitely due to a ReDoS vulnerability during date parsing.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 12 Jul 2021
- **Updated:** 3 Aug 2024
- **Also known as:** ECHO-ae7e-bb92-3687, GHSA-9pq7-rcxv-47vq

## What is CVE-2021-27293?

CVE-2021-27293 is a high-severity denial of service vulnerability in n/a, published on 12 Jul 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

RestSharp < 106.11.8-alpha.0.13 uses a regular expression which is vulnerable to Regular Expression Denial of Service (ReDoS) when converting strings into DateTimes. If a server responds with a malicious string, the client using RestSharp will be stuck processing it for an exceedingly long time. Thus the remote server can trigger Denial of Service.

Weakness: CWE-697 (Incorrect Comparison)

## Which versions are affected by CVE-2021-27293?

2 open source packages ship an affected version, including RestSharp. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `RestSharp` | NuGet | All versions | 106.11.8-alpha.0.13 |
| `RestSharp` | NuGet | All versions | 106.11.8-alpha.0.13 |

Products: Restsharp Restsharp.

## How do I fix CVE-2021-27293?

Upgrade RestSharp to 106.11.8-alpha.0.13 or later.

## Is CVE-2021-27293 being exploited?

There is no known exploitation of CVE-2021-27293 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2024-45302](https://insights.sbomify.com/CVE-2024-45302/): CRLF Injection in RestSharp's `RestRequest.AddHeader` method (medium 6.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-27293 and fix it if it is affected.

What it is: CVE-2021-27293 is a high-severity denial of service vulnerability in n/a, published on 12 Jul 2021. 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-2021-27293 in the wild and no public exploit code.

Affected packages and fixed versions:
- RestSharp (NuGet): affected all versions; fixed in 106.11.8-alpha.0.13
- RestSharp (NuGet): affected all versions; fixed in 106.11.8-alpha.0.13

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-2021-27293/ (Markdown: https://insights.sbomify.com/CVE-2021-27293/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-27293
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-27293
- OSV: https://osv.dev/vulnerability/CVE-2021-27293

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-27293/
Summaries are generated and may contain mistakes; the official description above is the record.