CVE-2026-77166

Deferred Deferred - Pending Action

BaseFortify

Publication date: 2026-09-21

Last updated on: 2026-09-22

Assigner: HackerOne

Description

The emoji field in the page emoji update endpoint does not properly validate user input. By injecting long text and line breaks, the sidebar layout becomes broken and can hide other items.

CVSS Scores

EPSS Scores

Probability:
Percentile:

Meta Information

Published

2026-09-21

Last Modified

2026-09-22

Generated

2026-10-12

AI Q&A

2026-09-21

EPSS Evaluated

2026-10-11

NVD

CVE-2026-77166

EUVD

EUVD-2026-83972

Affected Vendors & Products

Vendor	Product	Version / Range
Nextcloud	Collectives	3.2.1

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-840	Business Logic Errors

Attack-Flow Graph

Executive Summary

The vulnerability involves improper input validation in the emoji field of a page emoji update endpoint. Attackers can inject long text with line breaks, causing the sidebar layout to break and potentially hide other interface elements.

Detection Guidance

This vulnerability involves improper input validation in the emoji field of a page emoji update endpoint, leading to layout issues. To detect it, monitor for unusual text inputs containing long strings or line breaks in the emoji field. Check server logs for malformed requests or layout errors in the sidebar. No specific commands are provided, but inspecting HTTP requests to the endpoint and validating input handling can help identify the issue.

Impact Analysis

This could lead to a degraded user experience where critical UI elements become inaccessible. It may also enable phishing attacks by manipulating the visible interface to trick users into interacting with hidden elements.

Compliance Impact

This vulnerability does not directly impact compliance with GDPR, HIPAA, or similar standards as it only affects the visual layout of the sidebar by breaking or hiding items due to improper input validation in the emoji field.

Mitigation Strategies

Validate and sanitize all user input in the emoji field to prevent long text and line breaks from breaking the sidebar layout. Implement input length restrictions and filter out unwanted characters.

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