CVE-2026-6276: stale custom cookie host causes cookie leak

High severity · published May 13, 2026

CVE-2026-6276

stale custom cookie host causes cookie leak

7.5

CVSS

0.3%

EPSS

On KEV

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.

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack vector

Network

Complexity

Low

Privileges

None

User interaction

None

Confidentiality

None

Integrity

None

Availability

High

Scope

Unchanged

Exploitation

Is it being used?

Exploit prediction (EPSS)0.3% · higher than 22% of CVEs

Exploited in the wildNo evidence yet

CISA KEVNot listed

Ransomware campaign useNot known

Affected products

Which versions

curl · curl

7.71.0 before 8.14.2; 8.15.0 before 8.16.1; 8.17.0 before 8.20.0; e15e51384a423be31318b3c9c7d612a1aae661fd before 3a19987a87f393d9394fe5acc7643f6c263c92db; 8.19.0; 8.18.0; +34 more · source: vendor, NVD

In the news

VulnerabilityHigh

Hitachi Energy RTU500 Product

View CSAF Summary Hitachi Energy is aware of vulnerabilities that affect RTU500 product versions listed in this document. These vulnerabilities if exploited can have impact on confidentiality, integrity and availability of the product. Please refer to the Recommended Immediate Actions for information about the mitigation/remediation. The following versions of Hitachi Energy RTU500 Product are affected: RTU500 series CMU Firmware vers:RTU500_series_CMU_Firmware/>=13.5.1|<=13.5.4, vers:RTU500_series_CMU_Firmware/>=13.6.1|<=13.6.3, vers:RTU500_series_CMU_Firmware/>=13.7.1|<=13.7.8, vers:RTU500_series_CMU_Firmware/>=13.8.1|<=13.8.2, vers:RTU500_series_CMU_Firmware/>=12.7.1|<=12.7.7 (CVE-2026-17539, CVE-2026-28388, CVE-2026-6732, CVE-2026-6653, CVE-2026-6276, CVE-2026-9079, CVE-2026-11856, CVE-2026-8927, CVE-2026-8932, CVE-2026-17539, CVE-2026-28388, CVE-2026-6732, CVE-2026-6653, CVE-2026-6276, CVE-2026-9079, CVE-2026-11856, CVE-2026-8927, CVE-2026-8932, CVE-2026-17539, CVE-2026-28388, CVE-2026-6732, CVE-2026-6653, CVE-2026-6276, CVE-2026-9079, CVE-2026-11856, CVE-2026-8927, CVE-2026-8932, CVE-2026-17539, CVE-2026-28388, CVE-2026-6732, CVE-2026-6653, CVE-2026-6276, CVE-2026-9079, CVE-2026-11856, CVE-2026-8927, CVE-2026-8932, CVE-2026-17539, CVE-2026-28388, CVE-2026-6653) CVSS Vendor Equipment v3 8.8 Hitachi Energy RTU500 series CMU Firmware 7 Vulnerabilities NULL Pointer Dereference, ...

CVE-2026-17539 CVE-2026-28388 CVE-2026-6732

Oct 20, 2026·US-CERT ICS Advisories

Affected product

curl

All curl CVEs

References

NVD

https://nvd.nist.gov/vuln/detail/CVE-2026-6276

CVE.org

https://www.cve.org/CVERecord?id=CVE-2026-6276

Patch

https://curl.se/docs/CVE-2026-6276.html

Product

https://curl.se/docs/CVE-2026-6276.json

Exploit

https://hackerone.com/reports/3671818

Mailing List

http://www.openwall.com/lists/oss-security/2026/04/29/13