How severe is CVE-2021-43805?

CVE-2021-43805 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2021-43805?

CVE-2021-43805 affects the following packages: solidus_core (RubyGems), solidus_core (RubyGems), solidus_core (RubyGems). Ecosystems affected: RubyGems.

How do I fix CVE-2021-43805?

Update solidus_core to 2.11.13 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-43805 is resolved across your whole dependency graph.

How do I detect CVE-2021-43805 in my RubyGems dependencies?

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

How do I mitigate CVE-2021-43805 if there is no patch (or I can't update yet)?

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.

Is CVE-2021-43805 actively exploited in the wild?

Yes. There are 1 known exploit references for CVE-2021-43805, including 1 in-the-wild exploitation observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2021-43805?

CVE-2021-43805 has an EPSS (Exploit Prediction Scoring System) score of 1.4%, placing it in the 73th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2021-43805?

CVE-2021-43805 is classified as CWE-1333 (CWE-1333). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2021-43805 published, and has it been updated?

CVE-2021-43805 was published on December 7, 2021 and was last updated on July 9, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

💎

💎 RubyGems

Not in CISA KEV

HIGH severity

CVE-2021-43805 — solidus_core

HIGHFix: solidusio/solidus@9867153

CVE-2021-43805 is a high-severity (CVSS 7.5) CWE-1333 vulnerability in solidus_core. 1 public exploit reference exists, so weaponization risk is real. A fix is available for solidus_core — see the affected versions and patch details below.

ReDos vulnerability on guest checkout email validation

Also known asGHSA-qxmr-qxh6-2cc9

Published

Dec 7, 2021

Updated

Jul 9, 2026

Affected

3 pkgs

Patched

3 / 3

Exploits

1 known

Exploitation data as of Oct 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

1.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs73th percentile — riskier than 73% of all scored CVEsHighest risk

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

How urgent is this, really

CVE-2021-43805 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,386 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

3 pkgs affected

💎solidus_core💎solidus_core💎solidus_core

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

Description

Impact

Denial of service vulnerability that could be exploited during a guest checkout. The regular expression used to validate a guest order's email was subject to exponential backtracking through a fragment like a.a..

Before the patch, it can be reproduced in the console like this:

irb(main)> Spree::EmailValidator::EMAIL_REGEXP.match "[email protected].@"
processing time: 54.293660s
=> nil

To reproduce in the browser, fill in the "Customer Email" field with that fake email address during a guest checkout. Before that, you should open the browser dev tools and change the type attribute for that field from email to text. After entering a fake address and pressing the "Save & Continue" button, the browser will take a long term to perform the request before showing an error message for the invalid address. Eventually, making the email string even longer could lead to the exhaustion of server resources.

Patches

Versions 3.1.4, 3.0.4, and 2.11.13 have been patched to use a different regular expression.

There's an improbable chance that some orders in your system end up having associated an email address that is no longer valid. We've added a task to check precisely that:

bin/rails solidus:check_orders_with_invalid_email

The above will print information for every affected order if any.

Workarounds

If a prompt upgrade is not an option, please, add the following to config/application.rb:

config.after_initialize do
  Spree::EmailValidator.send(:remove_const, :EMAIL_REGEXP)
  Spree::EmailValidator::EMAIL_REGEXP = URI::MailTo::EMAIL_REGEXP
end

References

For more information

If you have any questions or comments about this advisory:

Open an issue or a discussion in Solidus.
Email us at [email protected]
Contact the core team on Slack

Affected Packages

3 total 3 fixed

Ecosystem	Package	Vulnerable range	Fix
💎RubyGems	`solidus_core`	all versions	2.11.13`bundle update solidus_core --conservative`
💎RubyGems	`solidus_core`	≥ 3.0.0&&< 3.0.4	3.0.4`bundle update solidus_core --conservative`
💎RubyGems	`solidus_core`	≥ 3.1.0&&< 3.1.4	3.1.4`bundle update solidus_core --conservative`

Affected Products

1 product · 3 configurations

Application

solidusnebulab

≥ 3.1.0 && < 3.1.4

range

Exploits & PoCs

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

Solidus is a free, open-source ecommerce platform built on Rails. Versio…

github.comNVDDec 2021

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for solidus_core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update solidus_core to 2.11.13 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-43805 is resolved across your whole dependency graph.
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

### Impact Denial of service vulnerability that could be exploited during a guest checkout. The regular expression used to validate a guest order's email was subject to exponential backtracking through a fragment like `a.a.`. Before the patch, it can be reproduced in the console like this: ```ruby irb(main)> Spree::EmailValidator::EMAIL_REGEXP.match "[email protected].@" processing time: 54.293660s => nil ``` To reproduce in the browser, fill in the "Customer Email" field with that fake email address during a guest checkout. Before that, you shoul