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CVE-2026-1525— undici is vulnerable to Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

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开源的一个HTTP/1.1客户端。 undici存在安全漏洞，该漏洞源于允许重复的HTTP Content-Length标头，可能导致生成具有多个冲突Content-Length值的畸形HTTP/1.1请求，引发拒绝服务或HTTP请求夹带攻击。

CVSS 6.5 · Medium EPSS 0.49% · P40
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I. Basic Information for CVE-2026-1525

Vulnerability Information
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Vulnerability Title
undici is vulnerable to Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Source: CVE Program / CVE List V5
Vulnerability Description
Undici allows duplicate HTTP Content-Length headers when they are provided in an array with case-variant names (e.g., Content-Length and content-length). This produces malformed HTTP/1.1 requests with multiple conflicting Content-Length values on the wire. Who is impacted: * Applications using undici.request(), undici.Client, or similar low-level APIs with headers passed as flat arrays * Applications that accept user-controlled header names without case-normalization Potential consequences: * Denial of Service: Strict HTTP parsers (proxies, servers) will reject requests with duplicate Content-Length headers (400 Bad Request) * HTTP Request Smuggling: In deployments where an intermediary and backend interpret duplicate headers inconsistently (e.g., one uses the first value, the other uses the last), this can enable request smuggling attacks leading to ACL bypass, cache poisoning, or credential hijacking
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
HTTP请求的解释不一致性(HTTP请求私运)
Source: CVE Program / CVE List V5
Vulnerability Title
undici 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
undici是Node.js开源的一个HTTP/1.1客户端。 undici存在安全漏洞，该漏洞源于允许重复的HTTP Content-Length标头，可能导致生成具有多个冲突Content-Length值的畸形HTTP/1.1请求，引发拒绝服务或HTTP请求夹带攻击。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
undici undici < 6.24.0; 7.0.0 < 7.24.0 -

II. Public POCs for CVE-2026-1525

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III. Intelligence Information for CVE-2026-1525

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Vendor Advisories for CVE-2026-1525 (1)

Other References for CVE-2026-1525 (1)

Other References for CVE-2026-1525 (1)

Same Patch Batch · undici · 2026-03-12 · 6 CVEs total

CVE-2026-1526 7.5 HIGH undici is vulnerable to Unbounded Memory Consumption in undici WebSocket permessage-deflat
CVE-2026-1528 7.5 HIGH undici is vulnerable to Malicious WebSocket 64-bit length overflows undici parser and cras
CVE-2026-2229 7.5 HIGH undici is vulnerable to Unhandled Exception in undici WebSocket Client Due to Invalid serv
CVE-2026-2581 5.9 MEDIUM undici is vulnerable to Unbounded Memory Consumption in in Undici's DeduplicationHandler v
CVE-2026-1527 4.6 MEDIUM undici is vulnerable to CRLF Injection via upgrade option

IV. Related Vulnerabilities

Same product: undici
Same vendor: undici
Same weakness: CWE-444

V. Comments for CVE-2026-1525

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