What is CVE-2021-41134?

CVE-2021-41134 is a high-severity vulnerability in Jupyter Nbdime, classified under Cross-site Scripting. CVSS score: 8.7/10. Published 2021-11-03.

How severe is CVE-2021-41134?

High severity. CVSS v3 base score is 8.7 out of 10.

XSS in Jupyter Nbdime

CVE-2021-41134

nbdime provides tools for diffing and merging of Jupyter Notebooks. In affected versions a stored cross-site scripting (XSS) issue exists within the Jupyter-owned nbdime project. It appears that when reading the file name and path from disk, the extension does not sanitize the string it constructs before returning it to be displayed. The diffNotebookCheckpoint function within nbdime causes this issue. When attempting to display the name of the local notebook (diffNotebookCheckpoint), nbdime appears to simply append .ipynb to the name of the input file. The NbdimeWidget is then created, and the base string is passed through to the request API function. From there, the frontend simply renders the HTML tag and anything along with it. Users are advised to patch to the most recent version of the affected product.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2021-11-03 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 8.7 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N.

EPSS exploit prediction

EPSS: 0.007 (51.4th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 51st percentile — 51.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.007 · newest: 0.007 · change: 0.000

Affected products

Jupyter Nbdime — versions < 1.1.1 - nbdime (pip), >= 2.0.0 , < 2.1.1 - nbdime (pip), >= 3.0.0, < 3.1.1 - nbdime (pip)
Jupyter Nbdime-Jupyterlab

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

github.com/jupyter/nbdime/security/advisories/GHSA-p6rw-44q7-3fw4 (Third Party Advisory)
github.com/jupyter/nbdime/commit/e44a5cc7677f24b45ebafc756db49058c2f750ea (Patch, Third Party Advisory)

Frequently asked questions

What is CVE-2021-41134?: CVE-2021-41134 is a high-severity vulnerability in Jupyter Nbdime, classified under Cross-site Scripting. CVSS score: 8.7/10. Published 2021-11-03.
How severe is CVE-2021-41134?: High severity. CVSS v3 base score is 8.7 out of 10.