curl libcurl up to 8.21.0 Cookie Processing insertion of sensitive information into sent data

CVSS Meta Temp Score
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Current Exploit Price (≈)
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CTI Interest Score
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5.3$0-$5k2.37+

Summaryinfo

A vulnerability was found in curl libcurl. It has been rated as problematic. This issue affects some unknown processing of the component Cookie Processing. This manipulation causes insertion of sensitive information into sent data. The identification of this vulnerability is CVE-2026-82209. It is possible to initiate the attack remotely. There is no exploit available.

Detailsinfo

A vulnerability has been found in curl libcurl and classified as problematic. Affected by this vulnerability is an unknown function of the component Cookie Processing. The manipulation 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. The summary by CVE is:

When libpsl support is enabled, libcurl fails to enforce the Public Suffix List boundary check when processing a `Set-Cookie` header where the `Domain` attribute explicitly matches an origin host that is itself a public suffix (e.g., `Domain=co.uk` set by `co.uk`). Instead of coercing it into a strict host-only cookie, libcurl saves the cookie with wildcard domain scope (`.co.uk`). Consequently, the cookie is inappropriately included in subsequent outbound requests or HTTP redirects to arbitrary sibling subdomains under the same public suffix (e.g., `attacker.co.uk`).

The advisory is shared at curl.se. This vulnerability is known as CVE-2026-82209 since 08/28/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. 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 09/06/2026). 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.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-72153). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Type

Vendor

Name

Version

License

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.3
VulDB Meta Temp Score: 5.3

VulDB Base Score: 5.3
VulDB Temp Score: 5.3
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

08/28/2026 CVE reserved
09/06/2026 +9 days Advisory disclosed
09/06/2026 +0 days VulDB entry created
09/06/2026 +0 days VulDB entry last update

Sourcesinfo

Advisory: curl.se
Status: Confirmed

CVE: CVE-2026-82209 (🔒)
GCVE (CVE): GCVE-0-2026-82209
GCVE (VulDB): GCVE-100-399469
EUVD: 🔒

Entryinfo

Created: 09/06/2026 20:08
Updated: 09/06/2026 21:45
Changes: 09/06/2026 20:08 (53), 09/06/2026 21:45 (1)
Complete: 🔍
Cache ID: 216::103

If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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