CVE-2021-39286

Cross-site scripting in pywb

6.1 MediumFix available

Webrecorder pywb before 2.6.0 allows XSS because it does not ensure that Jinja2 templates are autoescaped.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: Required

What an attacker can affect

Confidentiality: Low
Integrity: Low
Availability: None

Exploit likelihood

0.70%Unchanged since Aug 19, 2021

What each source reports

NVD Score used 6.1

Webrecorder pywb before 2.6.0 allows XSS because it does not ensure that Jinja2 templates are autoescaped.

Record: CVE-2021-39286
CVSS 3.1: 6.1 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
CVSS 2.0: 4.3 MediumAV:N/AC:M/Au:N/C:N/I:P/A:N
Weakness: CWE-79
Updated: 2026-11-02

CVE List No score

Webrecorder pywb before 2.6.0 allows XSS because it does not ensure that Jinja2 templates are autoescaped.

Record: CVE-2021-39286
Updated: 2026-11-02

EUVDEUVD-2021-0213 No score

Webrecorder pywb before 2.6.0 allows XSS because it does not ensure that Jinja2 templates are autoescaped.

Record: EUVD-2021-0213
Updated: 2026-11-03

GitHub AdvisoriesGHSA-947x-pv47-pp3q 5.3

Cross-site scripting in pywb

Webrecorder pywb before 2.6.0 allows XSS because it does not ensure that Jinja2 templates are autoescaped.

Record: GHSA-947x-pv47-pp3q
CVSS 4.0: 5.3 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
CVSS 3.1: 6.1 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Weakness: CWE-79
Updated: 2026-11-02

OSV 6.1

Webrecorder pywb before 2.6.0 allows XSS because it does not ensure that Jinja2 templates are autoescaped.

Record: CVE-2021-39286
CVSS 3.1: 6.1 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Updated: 2026-11-02

OSVGHSA-947x-pv47-pp3q 5.3

Cross-site scripting in pywb

Webrecorder pywb before 2.6.0 allows XSS because it does not ensure that Jinja2 templates are autoescaped.

Record: GHSA-947x-pv47-pp3q
CVSS 4.0: 5.3 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
CVSS 3.1: 6.1 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Weakness: CWE-79
Updated: 2026-11-02

OSVPYSEC-2021-120 No score

Webrecorder pywb before 2.6.0 allows XSS because it does not ensure that Jinja2 templates are autoescaped.

Record: PYSEC-2021-120
Updated: 2026-11-02

Affected products

webrecorder pywb

Affected packages

Affected packages
Package	Affected	Fixed
`pywb` PyPI	before 2.6.0	2.6.0
`pywb` PyPI	before 2.6.0, plus listed versions 0.10.00.10.10.10.100.10.20.10.5 Show 45 moreShow less 0.10.60.10.70.10.80.10.90.10.9.10.11.00.11.10.11.20.11.30.11.40.11.50.2.00.2.20.3.00.30.00.30.10.31.00.32.00.32.10.33.00.33.10.33.20.4.00.4.50.4.70.5.00.5.10.5.30.5.40.6.00.6.20.6.30.6.40.6.50.6.60.7.00.7.10.7.20.7.50.7.60.7.70.7.80.8.00.8.10.8.2	2.6.0

History

History
Recorded	Changed	Sources
Nov 3, 2026	aliases	EUVD
Nov 2, 2026	first indexed	CVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-39286 is a medium vulnerability (CVSS 6.1) in Webrecorder Pywb, published August 18, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.70%, the 53rd percentile. Fixed in pywb 2.6.0.

References

This page doesn't list everything

Left out here: 33 versions. The JSON record has them.