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CVE-2021-39286

21
FAUCET Score

CVE-2021-39286 is a medium-severity Cross-Site Scripting (XSS) vulnerability affecting Webrecorder pywb versions prior to 2.6.0, stemming from a lack of autoescaping in Jinja2 templates. This flaw allows an unauthenticated attacker to inject malicious scripts into a user's browser, requiring user interaction to succeed, and potentially leading to limited impact on confidentiality and integrity. There is no evidence of active exploitation, publicly available exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage regarding this vulnerability.

Impacted Technologies

VendorProductVersion(s)CPE
< 2.6.0CPE matchmatch criteria
cpe:2.3:a:webrecorder:pywb:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

6.1MEDIUM

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality Impact
LOW
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
2.8
Impact Score
2.7
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.70%
Probability of exploitation in next 30 days
EPSS Percentile
49.4%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0070 is in the 55th percentile among its peer group of 26,221 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (2)

github_advisorypatch availablevia nvd_reference
View patch
pippatch availablevia ghsa
Product: pywbFixed in: 2.6.0

Vendor Advisories (1)

pipGHSA-947x-pv47-pp3qmedium

Cross-site scripting in pywb

Sep 2, 2021

References

github.com / webrecorder/pywb/commit/f7bd84cdacdd665ff73ae8d09a202f60be2ebae9
PatchThird Party Advisory
github.com / webrecorder/pywb/compare/v-2.5.0...v-2.6.0
Release NotesThird Party Advisory