CVE-2026-6276
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…
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.29%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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 3.1
- 7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- EPSS
- 0.29% probability · 22th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-319
- Affected
- haxx/curl
- Source
- 2499f714-1537-4658-8207-48ae4bb9eae9
References
- https://curl.se/docs/CVE-2026-6276.htmlPatch, Vendor Advisory
- https://curl.se/docs/CVE-2026-6276.jsonProduct
- https://hackerone.com/reports/3671818Exploit, Issue Tracking, Third Party Advisory
- http://www.openwall.com/lists/oss-security/2026/04/29/13Mailing List, Third Party Advisory
- https://hackerone.com/reports/3671818Exploit, Issue Tracking, Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.