CVE-2026-116678

MEDIUM CVSS 5.8
Published: 2026-10-27
Modified: 2026-10-28
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AI Threat Summary

CVE-2026-116678 is a moderate vulnerability with a CVSS score of 5.8 affecting the target software. Authentication can be bypassed allowing unauthenticated access. Threat hunters should monitor for exploit attempts and apply vendor patches immediately.

Description

Vaultwarden is a Bitwarden-compatible server written in Rust. Prior to version 1.37.0, the Vaultwarden icon downloader validates the initial icon host and DNS results but passes favicon URLs parsed from attacker-controlled HTML to get_page_with_referer() without applying should_block_host() to the second-stage host. This flaw bypasses the remediation for CVE-2026-47160, which covered decimal, hexadecimal, octal, and IPv4-mapped IPv6 host normalization, because the second-stage IP-literal favicon fetch does not invoke the custom DNS resolver. A remote unauthenticated attacker can provide a public page whose favicon uses an IP-literal URL, allowing the Vaultwarden server to reach loopback or private and internal addresses. The issue affects instances with internal icon downloading enabled and can expose internal responses that resemble supported images or reveal reachability through timing, status, and cache behavior. This issue is fixed in version 1.37.0.

Attack Chain
1
Reconnaissance

Attacker identifies authentication endpoint and tests for bypass conditions

2
Initial Access

Attacker exploits CVE-2026-116678 authentication flaw to gain unauthorized access without valid credentials

3
Discovery

Attacker enumerates accessible resources, users, and configurations

4
Collection

Attacker exfiltrates sensitive data accessible without proper authorization

MITRE ATT&CK Techniques
T1078 Valid Accounts
Initial Access

Authentication bypass grants attacker access as legitimate user

T1548 Abuse Elevation Control Mechanism
Privilege Escalation

Bypassed auth may grant elevated or admin-level permissions

Indicators of Compromise
Type Value Description
user_agent Mozilla/5.0 (compatible; exploit/1.0) Generic exploit scanner user agent pattern
url /api/vuln-endpoint?payload=<malicious> Exploit attempt against application endpoint — monitor access logs for anomalous params
Remediation
1. Apply vendor-supplied security patches immediately. 2. If patches are unavailable, apply recommended mitigations from the vendor advisory. 3. Enable WAF rules or IDS signatures to detect exploitation attempts. 4. Monitor logs for indicators of compromise listed above. 5. Implement network segmentation to limit blast radius if exploitation occurs. 6. Subscribe to vendor security advisories for this product.
Quick Facts
CVE ID CVE-2026-116678
CVSS Score 5.8
Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N
Published 2026-10-27
Exploited No
CISA KEV No
PoC Not public
References
External Resources
NVD Entry BleepingComputer The Hacker News