CVE-2026-86409
stale SigV4 headers sent unintended
Description
Setting `CURLOPT_AWS_SIGV4` to NULL but does not disable SigV4 authentication, contrary to expectations and documentation. A subsequent transfer on the same handle still sends an `Authorization: AWS4-HMAC-SHA256` header to whatever URL isset next, leaking state information.
INFO
Published Date :
Oct. 20, 2026, 8:17 p.m.
Last Modified :
Oct. 20, 2026, 8:17 p.m.
Remotely Exploit :
No
Source :
2499f714-1537-4658-8207-48ae4bb9eae9
Solution
- Ensure AWS SigV4 is properly disabled.
- Update the library to the latest version.
- Avoid reusing transfer handles after disabling SigV4.
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-2026-86409.
| URL | Resource |
|---|---|
| https://curl.se/docs/CVE-2026-86409.html | |
| https://curl.se/docs/CVE-2026-86409.json | |
| https://hackerone.com/reports/3973135 |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-86409 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-2026-86409
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).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-86409 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-86409 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.
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New CVE Received by 2499f714-1537-4658-8207-48ae4bb9eae9
Oct. 20, 2026
Action Type Old Value New Value Added Description Setting `CURLOPT_AWS_SIGV4` to NULL but does not disable SigV4 authentication, contrary to expectations and documentation. A subsequent transfer on the same handle still sends an `Authorization: AWS4-HMAC-SHA256` header to whatever URL isset next, leaking state information. Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/86xxx/CVE-2026-86409.json">CVE-2026-86409</a> Added Reference https://curl.se/docs/CVE-2026-86409.html Added Reference https://curl.se/docs/CVE-2026-86409.json Added Reference https://hackerone.com/reports/3973135