# CVE-2026-53523: Nezha Monitoring: OAuth2 Redirect URL — Host Header Injection

> Attackers can inject malicious Host headers to redirect users to external sites during OAuth2 authentication, potentially leading to credential theft.

- **Severity:** Medium 6.8 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 12 Jun 2026
- **Updated:** 15 Jun 2026
- **Also known as:** GHSA-9rc6-8cjv-rcvx, GO-2026-5829

## What is CVE-2026-53523?

CVE-2026-53523 is a medium-severity vulnerability in nezhahq nezha, published on 12 Jun 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

Nezha Monitoring is a self-hostable, lightweight, servers and websites monitoring and O&M tool. From version 1.0.0 to before version 2.2.0, the getRedirectURL function in oauth2.go:22-29 constructs the OAuth2 callback URL by concatenating the request's Host header with a fixed path, with zero validation of the Host header. This can result in host header injection. This issue has been patched in version 2.2.0.

Weakness: CWE-601 (URL Redirection to Untrusted Site)

## Which versions are affected by CVE-2026-53523?

3 open source packages ship an affected version, including github.com/nezhahq/nezha.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/nezhahq/nezha` | Go | From 1.0.0 | None |
| `github.com/nezhahq/nezha` | Go | From 1.0.0 | 2.2.0 |
| `github.com/nezhahq/nezha` | Go | From 1.0.0 | 2.2.0 |

## How do I fix CVE-2026-53523?

Upgrade github.com/nezhahq/nezha to 2.2.0 or later.

## Is CVE-2026-53523 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-53523 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-53523 and fix it if it is affected.

What it is: CVE-2026-53523 is a medium-severity vulnerability in nezhahq nezha, published on 12 Jun 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-53523 exists.

Affected packages and fixed versions:
- github.com/nezhahq/nezha (Go): affected from 1.0.0; no fix listed
- github.com/nezhahq/nezha (Go): affected from 1.0.0; fixed in 2.2.0
- github.com/nezhahq/nezha (Go): affected from 1.0.0; fixed in 2.2.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-53523/ (Markdown: https://insights.sbomify.com/CVE-2026-53523/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53523
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53523
- OSV: https://osv.dev/vulnerability/CVE-2026-53523

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-53523/
Summaries are generated and may contain mistakes; the official description above is the record.