CVE-2026-6276
stale custom cookie host causes cookie leak
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.
INFO
Published Date :
May 13, 2026, 1:01 p.m.
Last Modified :
May 14, 2026, 2:21 p.m.
Remotely Exploit :
Yes !
Source :
2499f714-1537-4658-8207-48ae4bb9eae9
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | ||||
| CVSS 3.1 | HIGH | [email protected] |
Solution
- Clear cookies associated with the easy handle.
- Ensure Host header is reset for new requests.
- Re-initialize handle if stale cookies persist.
Public PoC/Exploit Available at Github
CVE-2026-6276 has a 3 public
PoC/Exploit available at Github.
Go to the Public Exploits tab to see the list.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-6276.
| URL | Resource |
|---|---|
| https://curl.se/docs/CVE-2026-6276.html | Patch Vendor Advisory |
| https://curl.se/docs/CVE-2026-6276.json | Product |
| https://hackerone.com/reports/3671818 | Exploit Issue Tracking Third Party Advisory |
| http://www.openwall.com/lists/oss-security/2026/04/29/13 | Mailing List Third Party Advisory |
| https://hackerone.com/reports/3671818 | Exploit Issue Tracking Third Party Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-6276 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-6276
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
RAD Security Image Scanner
Dockerfile Makefile Go
None
Dockerfile Makefile Shell Python
None
Shell Python
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-6276 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-6276 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
May. 14, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added CWE CWE-319 Added CPE Configuration OR *cpe:2.3:a:haxx:curl:*:*:*:*:*:*:*:* versions from (including) 7.71.0 up to (excluding) 8.20.0 Added Reference Type CVE: http://www.openwall.com/lists/oss-security/2026/04/29/13 Types: Mailing List, Third Party Advisory Added Reference Type curl: https://curl.se/docs/CVE-2026-6276.html Types: Patch, Vendor Advisory Added Reference Type curl: https://curl.se/docs/CVE-2026-6276.json Types: Product Added Reference Type CISA-ADP: https://hackerone.com/reports/3671818 Types: Exploit, Issue Tracking, Third Party Advisory Added Reference Type curl: https://hackerone.com/reports/3671818 Types: Exploit, Issue Tracking, Third Party Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
May. 13, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added Reference https://hackerone.com/reports/3671818 -
New CVE Received by 2499f714-1537-4658-8207-48ae4bb9eae9
May. 13, 2026
Action Type Old Value New Value Added 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. Added Reference https://curl.se/docs/CVE-2026-6276.html Added Reference https://curl.se/docs/CVE-2026-6276.json Added Reference https://hackerone.com/reports/3671818 -
CVE Modified by af854a3a-2127-422b-91ae-364da2661108
May. 13, 2026
Action Type Old Value New Value Added Reference http://www.openwall.com/lists/oss-security/2026/04/29/13