Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HSummary
CVE-2026-27944 is a critical-severity Missing Authentication for Critical Function (CWE-306) vulnerability in Nginxui Nginx Ui. Its CVSS base score is 9.8 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked in the top 3% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified map to AC-14 (Permitted Actions Without Identification or Authentication) and IA-2 (Identification and Authentication (Organizational Users)) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-27944 affects Nginx UI, a web user interface for the Nginx web server, in versions prior to 2.3.3. The vulnerability resides in the /api/backup endpoint, which is accessible without authentication and exposes encryption keys needed to decrypt backups via the X-Backup-Security response header. This flaw, linked to CWE-306 (Missing Authentication for Critical Function) and CWE-311 (Missing Encryption of Sensitive Data), enables attackers to retrieve and immediately decrypt full system backups containing highly sensitive information such as user credentials, session tokens, SSL private keys, and Nginx configurations. It carries a CVSS v3.1 base score of 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H), indicating critical severity.
Any unauthenticated remote attacker with network access to the Nginx UI instance can exploit this vulnerability. By simply sending a request to the /api/backup endpoint, the attacker receives both the encrypted backup file and the decryption key in the response header, allowing immediate access to all contained sensitive data without further privileges or user interaction.
The issue has been addressed in Nginx UI version 2.3.3, where authentication requirements and key exposure were fixed. Additional details are available in the GitHub Security Advisory at https://github.com/0xJacky/nginx-ui/security/advisories/GHSA-g9w5-qffc-6762.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-9847
Vulnerability Data
Nginx UI is a web user interface for the Nginx web server. Prior to version 2.3.3, the /api/backup endpoint is accessible without authentication and discloses the encryption keys required to decrypt the backup in the X-Backup-Security response header. This allows…
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an unauthenticated attacker to download a full system backup containing sensitive data (user credentials, session tokens, SSL private keys, Nginx configurations) and decrypt it immediately. This issue has been patched in version 2.3.3.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 13 hardening rules · 7 OS baselines
V6.2.3V6.4.4V10.4.16V12.1.3
Mitigating Controls (NIST 800-53 r5) AI
Directly mandates unique identification and authentication of users before access to functions requiring identity.
Extends the same authentication requirement to non-organizational users accessing critical functionality.
Requires authentication of services before they can invoke or expose critical functions.
SC-13 mandates use of specific cryptography, structurally preventing unencrypted sensitive data.
Explicitly identifies and limits actions permitted without authentication, preventing critical functions from being exposed.
SC-28 requires cryptographic protection of information at rest, eliminating the storage half of the weakness.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Directly requires authentication of users/services/hardware, which eliminates missing authentication for critical functions.
PR.DS-01 directly mandates encryption for data-at-rest and therefore prevents CWE-311 mostly for storage, yet the weakness also spans transmission and other contexts that this single at-rest control leaves unaddressed.
Managing identities and credentials is a prerequisite for authentication but does not itself enforce it on critical functions.
Defining and enforcing authorizations assumes prior authentication and therefore only partially mitigates the absence of authentication.
PR.DS-02 directly eliminates the transmission facet of CWE-311 via mandatory encryption but leaves the storage facet untouched, so each direction rates only partial.
Protecting networks from unauthorized access can be undermined by missing authentication but does not address the root authentication gap.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
The control explicitly calls for authentication before any critical function is reached, eliminating the possibility of bypassing authentication for high-value operations.
Explicit rules requiring encryption for sensitive information in transit eliminate the weakness of sending data without cryptographic protection.
Mandating authentication requirements for critical functions at the requirements-gathering stage ensures that essential operations are not left unprotected by missing login or verification mechanisms.
Mandating authentication for network services and critical functions stops attackers from invoking sensitive operations without credentials, closing gaps where authentication is absent for important capabilities.
Explicitly calling for protection of data in transit and at rest, plus secure encryption of communications, drives the implementation of encryption that prevents clear-text exposure of sensitive information.
Security engineering principles insist on authentication and authorization for every critical function, eliminating entry points that lack any access control mechanism.
Hardening callouts derived
Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).
Oracle Linux 8 (3 rules)
- V-248525 All OL 8 local disk partitions must implement cryptographic mechanisms to prevent unauthorized disclosure or modification of all information that requires at-rest protection. prevents CWE-311
- V-248585 OL 8 must require reauthentication when using the "sudo" command. prevents CWE-306
- V-248827 OL 8 must not have the rsh-server package installed. prevents CWE-306
Oracle Linux 9 (1 rule)
- V-271756 OL 9 local disk partitions must implement cryptographic mechanisms to prevent unauthorized disclosure or modification of all information that requires at rest protection. prevents CWE-311
RHEL 7 (2 rules)
- V-204442 The Red Hat Enterprise Linux operating system must not have the rsh-server package installed. prevents CWE-306
- V-237635 The Red Hat Enterprise Linux operating system must require re-authentication when using the "sudo" command. prevents CWE-306
RHEL 8 (3 rules)
- V-230492 RHEL 8 must not have the rsh-server package installed. prevents CWE-306
- V-230224 All RHEL 8 local disk partitions must implement cryptographic mechanisms to prevent unauthorized disclosure or modification of all information that requires at rest protection. prevents CWE-311
- V-237643 RHEL 8 must require re-authentication when using the "sudo" command. prevents CWE-306
RHEL 9 (1 rule)
- V-257879 RHEL 9 local disk partitions must implement cryptographic mechanisms to prevent unauthorized disclosure or modification of all information that requires at rest protection. prevents CWE-311
Windows Server 2016 (1 rule)
- V-224843 Systems requiring data at rest protections must employ cryptographic mechanisms to prevent unauthorized disclosure and modification of the information at rest. prevents CWE-311
Windows Server 2019 (1 rule)
- V-205727 Windows Server 2019 systems requiring data at rest protections must employ cryptographic mechanisms to prevent unauthorized disclosure and modification of the information at rest. prevents CWE-311