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CVE-2026-87018— undici vulnerable to Denial of Service via TLS 1.2 certificate-changing renegotiation

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。在以下版本中：4.2.1 至 6.29.0、7.0.0 至 7.30.0、以及 8.0.0 至 8.12.1，当 TLS 1.2 服务器在连接建立后发起重新协商（renegotiation），并提供一个不同但由受信任的 CA 签发的证书，且该证书的主机名（hostname）与请求的主机不匹配时，客户端进程会发生崩溃。 Node.js 会在重新协商过程中重新执行主机名验证，若验证失败，则会销毁 socket 并抛出“certificate-altname”错误

CVSS 7.5 · High

Affected Version Matrix 6

VendorProduct Version RangeStatus
undici undici 4.2.1< 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-2026-87018

Vulnerability Information
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Vulnerability Title
undici vulnerable to Denial of Service via TLS 1.2 certificate-changing renegotiation
Source: CVE Program / CVE List V5
Vulnerability Description
undici is an HTTP client library for Node.js. In versions 4.2.1 through 6.29.0, 7.0.0 through 7.30.0, and 8.0.0 through 8.12.1, the client process crashes when a TLS 1.2 server renegotiates after the connection is established and presents a different, CA-trusted certificate whose hostname does not match the requested host. Node.js re-runs hostname verification on the renegotiated handshake and destroys the socket with a certificate-altname error, but undici's established-socket error handler asserted that this error code could never occur, so the peer-controlled error became an uncaught assertion that terminates the Node.js process, affecting both the HTTP/1.1 and HTTP/2 paths. A malicious or compromised HTTPS endpoint reached through undici or the global fetch() can crash the client with a single server-initiated renegotiation, taking down all in-flight requests and background work in the process, and exploitation needs no CA compromise because the attacker controls the endpoint and can present two ordinary valid certificates. Only TLS 1.2 is affected, since TLS 1.3 does not support renegotiation. The issue is fixed in undici 6.29.1, 7.30.1, and 8.12.2, and users should upgrade to one of those versions or later. As a workaround, restrict outbound connections to TLS 1.3 so renegotiation cannot occur, when the target endpoints support it.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
未捕获的异常
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
undici undici 4.2.1 ~ 6.29.1 -

II. Public POCs for CVE-2026-87018

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III. Intelligence Information for CVE-2026-87018

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Vendor Advisories for CVE-2026-87018 (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-2026-109869 7.5 HIGH undici vulnerable to Denial of Service via unhandled error on excessive content-encodings
CVE-2026-109383 7.4 HIGH undici vulnerable to TLS certificate validation bypass via dropped tls options in Agent
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-248

V. Comments for CVE-2026-87018

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