stale custom cookie host causes cookie leak
Summary
| CVE | CVE-2026-6276 |
|---|---|
| State | PUBLISHED |
| Assigner | curl |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-05-13 13:01:56 UTC |
| Updated | 2026-05-14 14:21:06 UTC |
| Description | Using libcurl, when a custom `Host:` header is first set for an HTTP request and a second request is subsequently done using the same *easy handle* but without the custom `Host:` header set, the second request would use stale information and pass on cookies meant for the first host in the second request. Leak them. |
Risk And Classification
Primary CVSS: v3.1 7.5 HIGH from [email protected]
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS: 0.000130000 probability, percentile 0.020930000 (date 2026-05-25)
Problem Types: CWE-319 | CWE-346 Origin Validation Error
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | [email protected] | Primary | 7.5 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| 3.1 | ADP | DECLARED | 7.5 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| 3.1 | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | Secondary | 7.5 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
CVSS v3.1 Breakdown
Attack Vector
NetworkAttack Complexity
LowPrivileges Required
NoneUser Interaction
NoneScope
UnchangedConfidentiality
NoneIntegrity
NoneAvailability
HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD Known Affected Configurations (CPE 2.3)
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Curl | Curl | affected 8.19.0 8.19.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.18.0 8.18.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.17.0 8.17.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.16.0 8.16.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.15.0 8.15.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.14.1 8.14.1 semver | Not specified |
| CNA | Curl | Curl | affected 8.14.0 8.14.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.13.0 8.13.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.12.1 8.12.1 semver | Not specified |
| CNA | Curl | Curl | affected 8.12.0 8.12.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.11.1 8.11.1 semver | Not specified |
| CNA | Curl | Curl | affected 8.11.0 8.11.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.10.1 8.10.1 semver | Not specified |
| CNA | Curl | Curl | affected 8.10.0 8.10.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.9.1 8.9.1 semver | Not specified |
| CNA | Curl | Curl | affected 8.9.0 8.9.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.8.0 8.8.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.7.1 8.7.1 semver | Not specified |
| CNA | Curl | Curl | affected 8.7.0 8.7.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.6.0 8.6.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.5.0 8.5.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.4.0 8.4.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.3.0 8.3.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.2.1 8.2.1 semver | Not specified |
| CNA | Curl | Curl | affected 8.2.0 8.2.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.1.2 8.1.2 semver | Not specified |
| CNA | Curl | Curl | affected 8.1.1 8.1.1 semver | Not specified |
| CNA | Curl | Curl | affected 8.1.0 8.1.0 semver | Not specified |
| CNA | Curl | Curl | affected 8.0.1 8.0.1 semver | Not specified |
| CNA | Curl | Curl | affected 8.0.0 8.0.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.88.1 7.88.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.88.0 7.88.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.87.0 7.87.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.86.0 7.86.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.85.0 7.85.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.84.0 7.84.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.83.1 7.83.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.83.0 7.83.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.82.0 7.82.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.81.0 7.81.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.80.0 7.80.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.79.1 7.79.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.79.0 7.79.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.78.0 7.78.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.77.0 7.77.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.76.1 7.76.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.76.0 7.76.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.75.0 7.75.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.74.0 7.74.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.73.0 7.73.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.72.0 7.72.0 semver | Not specified |
| CNA | Curl | Curl | affected 7.71.1 7.71.1 semver | Not specified |
| CNA | Curl | Curl | affected 7.71.0 7.71.0 semver | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| hackerone.com/reports/3671818 | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | hackerone.com | Exploit, Issue Tracking, Third Party Advisory |
| curl.se/docs/CVE-2026-6276.json | 2499f714-1537-4658-8207-48ae4bb9eae9 | curl.se | Product |
| www.openwall.com/lists/oss-security/2026/04/29/13 | af854a3a-2127-422b-91ae-364da2661108 | www.openwall.com | Mailing List, Third Party Advisory |
| curl.se/docs/CVE-2026-6276.html | 2499f714-1537-4658-8207-48ae4bb9eae9 | curl.se | Patch, Vendor Advisory |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Muhamad Arga Reksapati (en)
CNA: Daniel Stenberg (en)
There are currently no legacy QID mappings associated with this CVE.