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CVE-2021-43827

MEDIUMCVSS 4.3/10EPSS 0.80%

Last modified

CVE-2021-43827 is a medium-severity vulnerability rated 4.3/10 on the CVSS scale. discourse-footnote is a library providing footnotes for posts in Discourse. ### Impact When posting an inline footnote wrapped in `<a>` tags (e.g. EPSS estimates a 0.80% chance of exploitation in the next 30 days.

Description

discourse-footnote is a library providing footnotes for posts in Discourse. ### Impact When posting an inline footnote wrapped in `<a>` tags (e.g. `<a>^[footnote]</a>`, the resulting rendered HTML would include a nested `<a>`, which is stripped by Nokogiri because it is not valid. This then caused a javascript error on topic pages because we were looking for an `<a>` element inside the footnote reference span and getting its ID, and because it did not exist we got a null reference error in javascript. Users are advised to update to version 0.2. As a workaround editing offending posts from the rails console or the database console for self-hosters, or disabling the plugin in the admin panel can mitigate this issue.

Metrics

CVSS 3.1
4.3/10

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L

EPSS Probability
0.80%

52.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
DiscourseDiscourse Footnote< 0.2

References

Timeline

Published
Last Modified
Status
Modified

Frequently Asked Questions

What is CVE-2021-43827?
discourse-footnote is a library providing footnotes for posts in Discourse. ### Impact When posting an inline footnote wrapped in `<a>` tags (e.g. `<a>^[footnote]</a>`, the resulting rendered HTML would include a nested `<a>`, which is stripped by Nokogiri because it is not valid. This then caused a javascript error on topic pages because we were looking for an `<a>` element inside the footnote reference span and getting its ID, and because it did not exist we got a null reference error in javascript. Users are advised to update to version 0.2. As a workaround editing offending posts from the rails console or the database console for self-hosters, or disabling the plugin in the admin panel can mitigate this issue.
How severe is CVE-2021-43827?
CVE-2021-43827 has a CVSS score of 4.3/10 (MEDIUM severity). The EPSS model estimates a 0.80% probability of exploitation in the next 30 days.
How do I fix CVE-2021-43827?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-43827?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST