How severe is CVE-2023-23621?

CVE-2023-23621 has a CVSS 3.x base score of 8.6, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2023-23621 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (54th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2023-23621?

CVE-2023-23621 primarily affects Discourse. In total, 208 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2023-23621?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2023-23621 published?

CVE-2023-23621 was published on 2023-01-28 and last updated on 2026-06-17.

CVE-2023-23621

CVE-2023-23621 is a high-severity vulnerability in Discourse with a CVSS 3.x base score of 8.6. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-1333.

Key facts

Severity: High (CVSS 3.x base score 8.6)
EPSS exploit prediction: 1% (54th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-1333
Affected product: Discourse
Published: 2023-01-28
Last modified: 2026-06-17

Description

Discourse is an open-source discussion platform. Prior to version 3.0.1 on the `stable` branch and version 3.1.0.beta2 on the `beta` and `tests-passed` branches, a malicious user can cause a regular expression denial of service using a carefully crafted user agent. This issue is patched in version 3.0.1 on the `stable` branch and version 3.1.0.beta2 on the `beta` and `tests-passed` branches. There are no known workarounds.

Frequently asked questions

What is CVE-2023-23621?: Discourse is an open-source discussion platform. Prior to version 3.0.1 on the `stable` branch and version 3.1.0.beta2 on the `beta` and `tests-passed` branches, a malicious user can cause a regular expression denial of service using a carefully crafted user agent. This issue is patched in version 3.0.1 on the `stable` branch and version 3.1.0.beta2 on the `beta` and `tests-passed` branches. There are no known workarounds.
How severe is CVE-2023-23621?: CVE-2023-23621 has a CVSS 3.x base score of 8.6, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2023-23621 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (54th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2023-23621?: CVE-2023-23621 primarily affects Discourse. In total, 208 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2023-23621?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2023-23621 published?: CVE-2023-23621 was published on 2023-01-28 and last updated on 2026-06-17.

References

Affected products (208)

cpe:2.3:a:discourse:discourse:*:*:*:*:stable:*:*:*
cpe:2.3:a:discourse:discourse:1.1.0:beta1:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.1.0:beta2:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.1.0:beta3:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.1.0:beta4:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.1.0:beta5:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.1.0:beta6:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.1.0:beta6b:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.1.0:beta7:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.1.0:beta8:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.2.0:beta1:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.2.0:beta2:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.2.0:beta3:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.2.0:beta4:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.2.0:beta5:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.2.0:beta6:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.2.0:beta7:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.2.0:beta8:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.2.0:beta9:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.3.0:beta1:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.3.0:beta10:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.3.0:beta11:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.3.0:beta2:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.3.0:beta3:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.3.0:beta4:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.3.0:beta5:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.3.0:beta6:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.3.0:beta7:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.3.0:beta8:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.3.0:beta9:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.4.0:beta1:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.4.0:beta10:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.4.0:beta11:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.4.0:beta12:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.4.0:beta2:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.4.0:beta3:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.4.0:beta4:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.4.0:beta5:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.4.0:beta6:*:*:beta:*:*:*
cpe:2.3:a:discourse:discourse:1.4.0:beta7:*:*:beta:*:*:*

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