curl up to 8.21.0/8.22.0 insertion of sensitive information into sent data

Summaryinfo

A vulnerability identified as problematic has been detected in curl up to 8.21.0/8.22.0. This affects an unknown function. Performing a manipulation results in insertion of sensitive information into sent data. This vulnerability is identified as CVE-2026-86413. The attack can be initiated remotely. There is not any exploit available.

Detailsinfo

A vulnerability classified as problematic has been found in curl up to 8.21.0/8.22.0. This affects some unknown functionality. The manipulation with an unknown input leads to a insertion of sensitive information into sent data vulnerability. CWE is classifying the issue as 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. This is going to have an impact on confidentiality. The summary by CVE is:

When using an *ambient user* in a first transfer doing Negotiate authentication and asked to follow redirects, curl could pass on its credential details to an unrelated second origin when asked to redirect there.

It is possible to read the advisory at curl.se. This vulnerability is uniquely identified as CVE-2026-86413 since 09/07/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. It demands that the victim is doing some kind of user interaction. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 10/20/2026). The attack technique deployed by this issue is T1592 according to MITRE ATT&CK.

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

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-105279). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Type

• Network Utility Software

Name

• curl

Version

• 8.0
• 8.1
• 8.2
• 8.3
• 8.4
• 8.5
• 8.6
• 8.7
• 8.8
• 8.9
• 8.10
• 8.11
• 8.12
• 8.13
• 8.14
• 8.15
• 8.16
• 8.17
• 8.18
• 8.19
• 8.20
• 8.21
• 8.21.0
• 8.22.0

License

• open-source

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

CVSSv3info

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Exploitinginfo

Threat Intelligenceinfo

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Timelineinfo

Sourcesinfo

Entryinfo

Be aware that VulDB is the high quality source for vulnerability data.

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