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CVE-2026-109841— undici vulnerable to Subresource Integrity bypass via non-lowercase algorithm tokens

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 的一个 HTTP 客户端库。在版本 7.15.0 至 7.30.0 以及 8.0.0 至 8.12.1 中，其 fetch() 实现对子资源完整性（Subresource Integrity, SRI）元数据的验证存在缺陷：该实现通过将算法令牌与仅包含小写字母的集合进行匹配来验证 SRI，尽管 SRI 规范定义该令牌应以其 ASCII 小写形式为准。因此，一个有效但非全小写的令牌（例如大写或混合大小写的 SHA256 令牌）会被视为未知并被跳过。 当没有识别出任何受支持的算法时，u

CVSS 5.9 · Medium

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 4

VendorProduct Version RangeStatus
undici undici 7.15.0< 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-2026-109841

Vulnerability Information
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Vulnerability Title
undici vulnerable to Subresource Integrity bypass via non-lowercase algorithm tokens
Source: CVE Program / CVE List V5
Vulnerability Description
undici is an HTTP client library for Node.js. In versions 7.15.0 through 7.30.0 and 8.0.0 through 8.12.1, its fetch() implementation verifies Subresource Integrity metadata by matching the algorithm token against a lowercase-only set, even though the SRI specification defines the token by its ASCII-lowercase form, so a valid but non-lowercase token such as an uppercase or mixed-case SHA256 is treated as unknown and skipped. When no recognized algorithm remains, undici treats the integrity list as empty and accepts the response, so a server returning a body that does not match the pinned digest passes the check. An attacker who controls only the response body can therefore deliver attacker-controlled bytes to an application that pinned a valid uppercase or mixed-case SRI token, with no integrity error, affecting response integrity only. The issue is fixed in undici 7.30.1 and 8.12.2, which normalize the algorithm token to ASCII lowercase before validation, and users should upgrade to one of those versions or later. As a workaround, use lowercase algorithm tokens such as sha256, sha384, or sha512 in integrity metadata.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
大小写敏感处理不恰当
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
undici undici 7.15.0 ~ 7.30.1 -

II. Public POCs for CVE-2026-109841

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III. Intelligence Information for CVE-2026-109841

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Vendor Advisories for CVE-2026-109841 (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-2026-109383 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-2026-109924 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-178

V. Comments for CVE-2026-109841

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