CyberSecBulletin
CVE-2026-77550NVD status: Deferred

UniFi OS Server: Improper Neutralization of CRLF Sequences

Published Updated By the CyberSecBulletin desk

CVE-2026-77550 is a critical-severity improper neutralization of CRLF sequences vulnerability in UniFi OS Server from Ubiquiti, with a CVSS 3.1 base score of 10.0 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists version 5.1.37 as the first without the flaw, so updating UniFi OS Server to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.8% chance of exploitation within 30 days, higher than 57% of scored CVEs.

Patch this week

Critical severity: a successful attack would have severe impact.

What to do

  1. Update UniFi OS Server to 5.1.37 or a later version.
  2. Update Cloud Keys to 5.1.31 or a later version.
  3. Update Network Video Recorders to 5.1.31 or a later version.
  4. Read the advisory on community.ui.com for workarounds and exact fixed builds.
  5. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
UbiquitiUniFi OS Serverbefore 5.1.375.1.37
UbiquitiCloud Keysbefore 5.1.315.1.31
UbiquitiNetwork Video Recordersbefore 5.1.315.1.31
UbiquitiEnterprise Network Video Recordersbefore 5.1.315.1.31
UbiquitiEnterprise Network Attached Storagebefore 5.1.315.1.31
UbiquitiDream Machinesbefore 5.1.315.1.31
UbiquitiEnterprise Firewall Corebefore 5.1.315.1.31
UbiquitiDream Routersbefore 5.1.315.1.31
UbiquitiEnterprise Fortress Gatewaybefore 5.1.315.1.31
UbiquitiCloud Gatewaysbefore 5.1.315.1.31
UbiquitiDream Wallbefore 5.1.315.1.31
UbiquitiExpress 7before 5.1.315.1.31
UbiquitiNetwork Attached Storagebefore 5.1.325.1.32
UbiquitiExpressbefore 4.0.174.0.17

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
ChangedThe attack can reach beyond the vulnerable component into other systems.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H. Scored by CNA.

Official description

A malicious actor with access to the network could exploit an Improper Neutralization of CRLF Sequences vulnerability found in certain devices running UniFi OS to bypass authentication to such UniFi OS devices or instances.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Improper Neutralization of CRLF Sequences

The product uses CRLF (carriage return line feeds) as a special element, e.g. to separate lines or records, but it does not neutralize or incorrectly neutralizes CRLF sequences from inputs.

How developers prevent this class of flaw

  • Appropriately filter or quote CRLF sequences in user-controlled input.

More Improper Neutralization of CRLF Sequences vulnerabilities (CWE-93)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in UniFi OS Server

All UniFi OS Server vulnerabilities

Recent Improper Neutralization of CRLF Sequences vulnerabilities

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