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.NET
.NET NuGet
Not in CISA KEV
HIGH severity

CVE-2021-27293 — RestSharp

HIGHFix: restsharp/RestSharp@be39346

CVE-2021-27293 is a high-severity (CVSS 7.5) CWE-697 vulnerability in RestSharp. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for RestSharp — see the affected versions and patch details below.

Incorrect Regular Expression in RestSharp

Also known asGHSA-9pq7-rcxv-47vq
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
1 known
Exploitation data as of Nov 8, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.5%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs75th percentile — riskier than 75% of all scored CVEsHighest risk
0.00%0.67%1.34%2.01%0.4%1.5%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
.NETRestSharp

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet packages — download data is not available via public APIs for these ecosystems.

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.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
.NETNuGetRestSharpall versions106.11.8-alpha.0.13dotnet add package RestSharp --version 106.11.8-alpha.0.13

Affected Products

1 product · 9 configurations
Application
restsharprestsharp
≤ 106.11.7
1 version
106.11.8
Exploits & PoCs
1

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

RestSharp < 106.11.8-alpha.0.13 uses a regular expression which is vulne…

github.comNVDJul 2021

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for RestSharp, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update RestSharp to 106.11.8-alpha.0.13 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-27293 is resolved across your whole dependency graph.

  3. Workarounds

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

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.
O3 Security · Impact-Aware SCA

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CVE-2021-27293: RestSharp DoS — Fix Available