curl up to 8.21.0 AWS SigV4 Authentication CURLOPT_AWS_SIGV4 insertion of sensitive information into sent data

CVSS Meta Temp Score
CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.
Current Exploit Price (≈)
Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.
CTI Interest Score
Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
4.3$0-$5k0.43

Summaryinfo

A vulnerability labeled as problematic has been found in curl. This impacts an unknown function of the component AWS SigV4 Authentication. Executing a manipulation of the argument CURLOPT_AWS_SIGV4 can lead to insertion of sensitive information into sent data. This vulnerability is tracked as CVE-2026-86409. The attack can be launched remotely. No exploit exists.

Detailsinfo

A vulnerability classified as problematic was found in curl. This vulnerability affects an unknown part of the component AWS SigV4 Authentication. The manipulation of the argument CURLOPT_AWS_SIGV4 with an unknown input leads to a insertion of sensitive information into sent data vulnerability. The CWE definition for the vulnerability is CWE-201. The code transmits data to another actor, but a portion of the data includes sensitive information that should not be accessible to that actor. As an impact it is known to affect confidentiality. CVE summarizes:

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.

The advisory is shared for download at curl.se. This vulnerability was named CVE-2026-86409 since 09/07/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 10/20/2026). The MITRE ATT&CK project declares the attack technique as T1592.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Type

Name

Version

License

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 4.3
VulDB Meta Temp Score: 4.3

VulDB Base Score: 4.3
VulDB Temp Score: 4.3
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Insertion of sensitive information into sent data
CWE: CWE-201 / CWE-200 / CWE-284
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: no mitigation known
Status: 🔍

0-Day Time: 🔒

Timelineinfo

09/07/2026 CVE reserved
10/20/2026 +43 days Advisory disclosed
10/20/2026 +0 days VulDB entry created
10/20/2026 +0 days VulDB entry last update

Sourcesinfo

Advisory: curl.se
Status: Confirmed

CVE: CVE-2026-86409 (🔒)
GCVE (CVE): GCVE-0-2026-86409
GCVE (VulDB): GCVE-100-422992

Entryinfo

Created: 10/20/2026 22:27
Changes: 10/20/2026 22:27 (53)
Complete: 🔍
Cache ID: 216::103

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