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CVE-2026-109383— undici vulnerable to TLS certificate validation bypass via dropped tls options in Agent

Quick assessment

Affected
undici undici
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.

undici 是 Node.js 的 HTTP 客户端库。在版本 4.0.0 至 6.29.0、7.0.0 至 7.30.0 以及 8.0.0 至 8.12.1 中，其 Agent 调度器（Agent dispatcher）在将构造函数选项转发至每个按来源（per-origin）连接的池之前，会通过基于 JSON 的深度克隆机制处理这些选项。由于 JSON 格式无法表示函数，调用方提供的包含 回调函数的 选项会在到达 TLS 层之前被静默丢弃。因此，尽管某些 TLS 对等方的证书本应通过自定义的 回调被拒绝，但由于

CVSS 7.4 · High

Affected Version Matrix 6

VendorProduct Version RangeStatus
undici undici 4.0.0< 6.29.1 affected
6.29.1 unaffected
7.0.0< 7.30.1 affected
7.30.1 unaffected
8.0.0< 8.12.2 affected
8.12.2 unaffected
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I. Basic Information for CVE-2026-109383

Vulnerability Information
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Vulnerability Title
undici vulnerable to TLS certificate validation bypass via dropped tls options in Agent
Source: CVE Program / CVE List V5
Vulnerability Description
undici is an HTTP client library for Node.js. In versions 4.0.0 through 6.29.0, 7.0.0 through 7.30.0, and 8.0.0 through 8.12.1, its Agent dispatcher passes its constructor options through a JSON-based deep clone before forwarding them to each per-origin pool, and because JSON cannot represent functions, a caller-supplied tls option containing a checkServerIdentity callback is silently dropped before it reaches the TLS layer. As a result, a TLS peer whose certificate a custom checkServerIdentity was written to reject, but which passes Node's default hostname and chain checks, is silently accepted. Because Agent is the default dispatcher behind request, fetch, and setGlobalDispatcher, this affects the path most applications use, and EnvHttpProxyAgent is affected on its direct and no-proxy routes as well, while only applications that pass a function-valued tls option such as a custom checkServerIdentity for certificate or public-key pinning are at risk. The issue is fixed in undici 6.29.1, 7.30.1, and 8.12.2, which preserve the tls option outside the JSON clone so custom verification callbacks are forwarded unchanged, and users should upgrade to one of those versions or later. As a workaround, pass the TLS options through connect instead of tls, or for proxied destinations use requestTls and proxyTls.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
证书验证不恰当
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
undici undici 4.0.0 ~ 6.29.1 -

II. Public POCs for CVE-2026-109383

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III. Intelligence Information for CVE-2026-109383

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Other References for CVE-2026-109383 (1)

Same Patch Batch · undici · 2026-10-15 · 9 CVEs total

CVE-2026-109855 7.5 HIGH undici WebSocket client vulnerable to Denial of Service via failed HTTP/2 handshake
CVE-2026-87018 7.5 HIGH undici vulnerable to Denial of Service via TLS 1.2 certificate-changing renegotiation
CVE-2026-109869 7.5 HIGH undici vulnerable to Denial of Service via unhandled error on excessive content-encodings
CVE-2026-109829 7.4 HIGH undici vulnerable to cache poisoning and cross-user disclosure via cross-origin redirects
CVE-2026-87029 5.9 MEDIUM undici vulnerable to Denial of Service via unhandled exception in the decompress intercept
CVE-2026-109932 5.9 MEDIUM undici WebSocket client vulnerable to Denial of Service via unbounded automatic PONG buffe
CVE-2026-109841 5.9 MEDIUM undici vulnerable to Subresource Integrity bypass via non-lowercase algorithm tokens
CVE-2026-109924 5.9 MEDIUM undici vulnerable to Denial of Service via unbounded memory in the EventSource parser

IV. Related Vulnerabilities

Same product: undici
Same vendor: undici
Same weakness: CWE-295

V. Comments for CVE-2026-109383

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