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CVE-2026-21871

21
FAUCET Score

CVE-2026-21871 is a Cross-Site Scripting (XSS) vulnerability affecting NiceGUI versions 2.13.0 to 3.4.1. It arises when developers use ui.navigate.history.push() or ui.navigate.history.replace() with attacker-controlled input, allowing arbitrary JavaScript execution in the victim's browser due to improper escaping. This medium-severity vulnerability (CVSS 6.1) requires user interaction and network access, potentially leading to limited impact on confidentiality and integrity. There is currently no evidence of active exploitation, public exploit code, or significant community discussion, and it is not listed in CISA's KEV catalog.

Impacted Technologies

VendorProductVersion(s)CPE
>= 2.13.0, < 3.5.0CPE matchmatch criteria
cpe:2.3:a:zauberzeug:nicegui:*:*:*:*:*:*:*:*

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
0.24%
Probability of exploitation in next 30 days
EPSS Percentile
15.6%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0024 is in the 16th 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)

pippatch availablevia ghsa
Product: niceguiFixed in: 3.5.0
github_advisoryvendor investigatingvia nvd_reference
View patch

Vendor Advisories (1)

pipGHSA-7grm-h62g-5m97medium

NiceGUI is vulnerable to XSS via Unescaped URL in ui.navigate.history.push() / replace()

Jan 8, 2026

References

github.com / zauberzeug/nicegui/releases/tag/v3.5.0
Release Notes
github.com / zauberzeug/nicegui/security/advisories/GHSA-7grm-h62g-5m97
ExploitVendor Advisory