CVE-2021-39286: Webrecorder pywb before 2.6.0 allows XSS because it does not ensure that Jinja2 templates are autoescaped.

Q: How do I fix CVE-2021-39286?

pywb: upgrade to 2.6.0. Exact commands for each OS are on this page.

Q: Is CVE-2021-39286 being exploited?

CVE-2021-39286 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-39286 affect?

CVE-2021-39286 affects pywb. Severity is medium (CVSS 6.1). Webrecorder pywb before 2.6.0 allows XSS because it does not ensure that Jinja2 templates are autoescaped.

Q: How urgent is CVE-2021-39286?

Priority 35/100. No elevated risk signals yet.

Routine

MEDIUM 6.1UPGRADE

CVE-2021-39286 is a medium-severity flaw (CVSS 6.1) affecting pywb. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	6.1 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.7% (top 47%)
CISA exploited list	No
Weakness	CWE-79
Published	2021-08-18
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: webrecorder

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-08-18 18:15 UTCPublished CVE record published
2026-06-17 04:03 UTCUpdated Record last modified

webrecorder pywb UPGRADE

Affected: < 2.6.0

Fixed in: 2.6.0

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy pywb || rpm -q pywb || pywb --version

2. UPGRADE to 2.6.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade pywb

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade pywb

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-39286?

pywb: upgrade to 2.6.0. Exact commands for each OS are on this page.

Is CVE-2021-39286 being exploited?

CVE-2021-39286 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-39286 affect?

CVE-2021-39286 affects pywb. Severity is medium (CVSS 6.1). Webrecorder pywb before 2.6.0 allows XSS because it does not ensure that Jinja2 templates are autoescaped.

How urgent is CVE-2021-39286?

Priority 35/100. No elevated risk signals yet.

References

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