CVE-2026-33026: nginx-ui Backup Restore Allows Tampering with Encrypted Backups

Should you act?

Critical, preconditions apply

Severe if exploited, but exploitation needs conditions that may not apply to you. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
• EPSS 0.2%, percentile 11: FIRST’s model estimates a 0.2% chance of exploitation activity in the next 30 days, higher than 11% of all scored CVEs (low). EPSS is a probability, not a verdict.
• Needs an account (high (admin)). Exposure depends on who can log in.
• Only applies if your dependency tree includes github.com/0xJacky/Nginx-UI (Go) < 1.9.10-0.20260315015203-f61bcec547c0, fixed in 1.9.10-0.20260315015203-f61bcec547c0. Check your lockfile, including transitive dependencies.

What it is

Nginx UI is a web user interface for the Nginx web server. Prior to version 2.3.4, the nginx-ui backup restore mechanism allows attackers to tamper with encrypted backup archives and inject malicious configuration during restoration. This issue has been patched in version 2.3.4.

From the GitHub advisory

Summary The nginx-ui backup restore mechanism allows attackers to tamper with encrypted backup archives and inject malicious configuration during restoration.

Details The backup format lacks a trusted integrity root. Although files are encrypted, the encryption key and IV are provided to the client and the integrity metadata (hashinfo.txt) is encrypted using the same key. As a result, an attacker who can access the backup token can decrypt the archive, modify its contents, recompute integrity hashes, and re-encrypt the bundle.

Because the restore process does not enforce integrity verification and accepts backups even when hash mismatches are detected, the system restores attacker-controlled configuration even when integrity verification warnings are raised. In certain configurations this may lead to arbitrary command execution on the host.

The backup system is built around the following workflow:

1. Backup files are compressed into nginx-ui.zip and nginx.zip. 2. The files are encrypted using AES-256-CBC. 3. SHA-256 hashes of the encrypted files are stored in hashinfo.txt. 4. The hash file is also encrypted with the same AES key and IV. 5. The AES key and IV are provided to the client as a "backup security token".

Weakness type: CWE-312, CWE-347, CWE-354.

Product: github.com/0xJacky/Nginx-UI (Go) · Assigned by: GitHub_M · Published: 2026-03-30

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Attack requirements: none
• Privileges required: high (admin)
• User interaction: none

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation poc, automatable yes, technical impact total.
• FIRST EPSS (model of 2026-10-21): 0.21% probability of exploitation activity in the next 30 days; percentile 11.

Timeline

• 2026-03-30 — CVE record published by GitHub_M
• 2026-03-30 — GitHub-reviewed advisory GHSA-fhh2-gg7w-gwpq published (critical)
• 2026-03-31 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-fhh2-gg7w-gwpq github.com
2. CVE.org record CVE-2026-33026 cve.org
3. NVD entry CVE-2026-33026 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. github.com github.com
4. github.com github.com
5. pkg.go.dev pkg.go.dev

Critical Go advisories · Today’s Security Digest