CVE-2026-6276
Description
A flaw was found in libcurl. This vulnerability allows for information disclosure when a custom Host: header is used in an initial HTTP request, and a subsequent request reuses the same connection without specifying a new Host: header. This can lead to libcurl incorrectly sending cookies intended for the first host to the second host, resulting in a cookie leak. This issue is categorized as an Origin Validation Error (CWE-346). Exploitation typically requires specific debugging configurations.
Statement
This Low severity flaw affects libcurl when a custom Host: header is initially set for an HTTP request, and a subsequent request uses the same easy handle without a custom Host: header. This can lead to the second request sending cookies intended for the first host. The curl command-line tool is not affected by this issue. Exploitation typically requires specific debugging configurations, reducing its overall impact.
Mitigation
To mitigate this issue, avoid using custom `Host:` headers with libcurl, especially when reusing the same easy handle for multiple requests. This vulnerability primarily arises from specific debugging configurations.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 3.7 | 7.5 | 7.5 |
| Attack Vector | Network | Network | Network |
| Attack Complexity | High | Low | Low |
| Privileges Required | None | None | None |
| User Interaction | None | None | None |
| Scope | Unchanged | Unchanged | Unchanged |
| Confidentiality | Low | None | None |
| Integrity Impact | None | None | None |
| Availability Impact | None | High | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Access Control,Other
Technical Impact: Gain Privileges or Assume Identity; Varies by Context
An attacker can access any functionality that is inadvertently accessible to the source.
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