curl up to 8.21.0/8.22.0 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-$5k2.14

Summaryinfo

A vulnerability identified as problematic has been detected in curl up to 8.21.0/8.22.0. Affected by this vulnerability is an unknown functionality. The manipulation leads to insertion of sensitive information into sent data. This vulnerability is referenced as CVE-2026-87861. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability was found in curl up to 8.21.0/8.22.0 and classified as problematic. This issue affects some unknown functionality. The manipulation with an unknown input leads to a insertion of sensitive information into sent data vulnerability. Using CWE to declare the problem leads to 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. Impacted is confidentiality. The summary by CVE is:

When using ambient user credentials, an HTTP request directed to one origin may be dispatched over a connection previously authenticated via Negotiate for a different origin, leaving the request's intended credentials unused.

The advisory is shared at curl.se. The identification of this vulnerability is CVE-2026-87861 since 09/09/2026. The exploitation is known to be easy. The attack may be initiated remotely. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 10/20/2026). MITRE ATT&CK project uses the attack technique T1592 for this issue.

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
💳💳💳💳💳💳
💳💳💳💳💳💳
💳💳💳💳💳💳
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

09/09/2026 CVE reserved
10/20/2026 +41 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-2026-87861 (🔒)
GCVE (CVE): GCVE-0-2026-87861
GCVE (VulDB): GCVE-100-423005

Entryinfo

Created: 10/20/2026 22:49
Changes: 10/20/2026 22:49 (51)
Complete: 🔍
Cache ID: 216::103

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