EUVD-2026-11685
GHSA-2mjp-6q6p-2qxm
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A06:2025 - Insecure Design
ASVS 5.0
V4 - API and Web Service HTTP request consistency
|
| Impact | CVSS 6.5 (MEDIUM). Attack vector: Network. Complexity: Low. Privileges required: None. User interaction: None. |
| Exploit ScenarioDerived | An attacker could exploit this vulnerability to request smuggling attacks leading to ACL bypass, cache poisoning, or credential. |
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Alert meAnalysisAIv1 – Mar 12, 2026
Undici fails to normalize HTTP header names when processing arrays, allowing duplicate Content-Length headers with case-variant names (e.g., "Content-Length" and "content-length") to be sent in malformed requests. Applications using undici's low-level APIs with user-controlled header inputs are vulnerable to request rejection by strict HTTP parsers or potential HTTP request smuggling attacks if intermediaries and backend servers interpret conflicting header values inconsistently. No patch is currently available.
Earlier versions of this analysis (1)
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. [CVSS 6.5 MEDIUM]
RemediationAI
Monitor vendor advisories for a patch. Restrict network access to the affected service where possible.
Affected VersionsENISA
Affected Packages
Source: OSV (Open Source Vulnerabilities)
Affects your stack
Affects 1 package in npm
Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Technical ContextAI · show details
Classified as CWE-444 (HTTP Request/Response Smuggling). 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 conseque
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- Exploit and PoC references, threat intelligence from 22 sources
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Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
Primary rating from NVD.
CVSS VectorNVD
Lifecycle Timeline
2DescriptionCVE.org
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
Blast Radius
ecosystem impact- 28 npm packages depend on undici (16 direct, 23 indirect)
Ecosystem-wide dependent count for version 7.0.0.
Executive ViewAI
Organizations using Undici should be aware of notable risk from CVE-2026-1525 rated CVSS 6.5. Exploitation could compromise the security of affected deployments. Organizations should apply vendor updates when available and monitor for exploitation.
Apply vendor patch. If patching is delayed: restrict network access and enable monitoring.
Threat Intelligence Overview
NVD
CVE.org
EPSS
VulDB
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions.
Related Vulnerabilities in Undici WebSocket DoS and Protocol Vulnerabilities
View all 6Same weakness CWE-444 – HTTP Request/Response Smuggling
View allSame technique Denial Of Service
View allVendor StatusVendor
SUSE
Severity: Medium| Product | Status |
|---|---|
| SUSE Liberty Linux 10 | Fixed |
| SUSE Liberty Linux 8 | Fixed |
| SUSE Liberty Linux 9 | Fixed |
Exploit-DB