CVE-2021-43805 | ReDos vulnerability on guest checkout email validation

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Solidus is a free, open-source ecommerce platform built on Rails. Versions of Solidus prior to 3.1.4, 3.0.4, and 2.11.13 have a 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.` Versions 3.1.4, 3.0.4, and 2.11.13 have been patched to use a different regular expression. The maintainers added a check for email addresses that are no longer valid that will print information about any affected orders that exist. If a prompt upgrade is not an option, a workaround is available. It is possible to edit the file `config/application.rb` manually (with code provided by the maintainers in the GitHub Security Advisory) to check email validity.

Published: 2021-12-07 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]

Conclusion & alert: CVE-2021-43805 is rated High Exploit Risk (70.4/100): CVSS High severity, with medium exploitation likelihood (EPSS 1.40%). Core evidence: 1 public exploit reference(s) are indexed (Exploit-DB). EPSS rose +1.29% over the last day, indicating growing attacker interest. Mandatory action: Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2021-43805

EDB-ID Source Kind Published Link
nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-43805

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.12% 1.40% +1.29%
2 2025-11-21 0.35% 0.12% -0.24%
3 2025-11-18 0.35%

Full EPSS history (8 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-43805

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
3.9 3.6 [email protected]
5.0 2.0 MEDIUM
AV:N/AC:L/Au:N/C:N/I:N/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:P)
Partial availability impact.
10.0 2.9 [email protected]

Weakness enumeration for CVE-2021-43805

GitHub Security Advisory for CVE-2021-43805

GHSA-qxmr-qxh6-2cc9 · Severity: high · Ecosystem: rubygems — ReDos vulnerability on guest checkout email validation

Affected software / configurations for CVE-2021-43805

Vendor Product Version Raw CPE
nebulab solidus < 2.11.13 cpe:2.3:a:nebulab:solidus:*:*:*:*:*:*:*:*
nebulab solidus >= 3.0.0, < 3.0.4 cpe:2.3:a:nebulab:solidus:*:*:*:*:*:*:*:*
nebulab solidus >= 3.1.0, < 3.1.4 cpe:2.3:a:nebulab:solidus:*:*:*:*:*:*:*:*

References for CVE-2021-43805

cvelogic Threat Intelligence