CVE-2025-12999
Quick assessment
Affected
Eclipse Foundation Eclipse Open VSX
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.
在构建响应中的绝对 URL（包括下载链接、图标、静态资源和 API 地址）时，直接采用了请求头中的 、 和 ，而未验证发送方是否为受信任的代理；若这些头不存在，则回退使用客户端提供的 头。 这些响应会被缓存在不包含主机名的键下（例如：自 0.6.0 版本起的 、自 0.9.0 版本起的 、自 0.14.5 版本起的 、自 0.34.2 版本起的 ）。因此，单个携带伪造请求头的请求即可将攻击者选定的 URL 植入缓存条目中，从而在条目的有效期内（默认为一小时；若启用 ，则影响范围扩展至整个集群）提供给所有其他客户端。
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I. Basic Information for CVE-2025-12999
Vulnerability Information
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Vulnerability Title
N/A
Source: CVE Program / CVE List V5
Vulnerability Description
UrlUtil.getBaseUrl builds the absolute URLs in a response — download links, icons, asset and API URLs — from the X-Forwarded-Host, X-Forwarded-Proto and X-Forwarded-Prefix request headers, with no check on whether the sender was a trusted proxy, falling back to the client-supplied Host header.
Those responses are cached under keys that do not include the host (extension.json since 0.6.0, namespace.details.json since 0.9.0, sitemap since 0.14.5, latest.extension.version.vscode since 0.34.2). A single request carrying a forged header therefore places attacker-chosen URLs into an entry served to every other client for the lifetime of that entry — one hour by default, and cluster-wide where ovsx.redis.enabled is set.
The VSIX download URL, its signature URL and the public key URL are all derived from the same base URL, so extension signing does not limit the impact: an attacker who poisons an entry supplies the package, the signature over it, and the key used to verify it.
Exploitability depends on deployment topology. A server reachable directly by clients, or fronted by a proxy that relays the client's X-Forwarded-Host rather than overwriting it, is exploitable by an unauthenticated remote attacker. A proxy that overwrites the header is not.
An unauthenticated attacker can poison Open VSX's per-extension metadata cache with attacker-controlled download, signature, and public-key URLs by supplying a crafted X-Forwarded-Host header, causing downstream VS Code-compatible editors to fetch and install a malicious VSIX.
Workarounds (unpatched versions)
1. Configure the reverse proxy to set rather than relay X-Forwarded-Host, X-Forwarded-Proto and X-Forwarded-Prefix — note that nginx's $host is the client's Host header and is not a safe value.
2. Ensure the server is not reachable except through that proxy.
3. Flush the caches afterwards; poisoned entries survive the configuration change.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:L/SC:H/SI:H/SA:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Affected Products
| Vendor | Product | Affected Versions | CPE | Subscribe |
|---|---|---|---|---|
| Eclipse Foundation | Eclipse Open VSX | 0.6.0 ~ 1.1.2 | - |
|
II. Public POCs for CVE-2025-12999
| # | POC Description | Source Link | Shenlong Link |
|---|
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Patches & Fixes for CVE-2025-12999 (1)
Other References for CVE-2025-12999 (2)
IV. Related Vulnerabilities
V. Comments for CVE-2025-12999
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