VDB-399473 · CVE-2026-80255 · EUVD-2026-72151

curl up to 8.21.0 Cookie 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.
5.3	$0-$5k	3.16+

Summaryinfo

A vulnerability marked as problematic has been reported in curl up to 8.21.0. This affects an unknown function of the component Cookie Handler. The manipulation leads to insertion of sensitive information into sent data. This vulnerability is listed as CVE-2026-80255. The attack may be initiated remotely. There is no available exploit.

Detailsinfo

A vulnerability was found in curl up to 8.21.0. It has been rated as problematic. This issue affects an unknown code of the component Cookie Handler. 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:

A `Set-Cookie:` header using tab (horizontal tab, ASCII code 9) instead of space (ascii code 32) immediately before the `Secure` attribute causes curl to store the cookie without its Secure flag. The cookie might then wrongfully be sent over plaintext HTTP on subsequent requests to the same host.

The advisory is shared at curl.se. The identification of this vulnerability is CVE-2026-80255 since 08/26/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. 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-2026-72151). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Type

Network Utility Software

Name

curl

Version

License

open-source

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

AV	AC	Au	C	I	A
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳

Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock

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: 🔒

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: no mitigation known
Status: 🔍

0-Day Time: 🔒

Timelineinfo

08/26/2026 CVE reserved
09/06/2026 +11 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-2026-80255 (🔒)
GCVE (CVE): GCVE-0-2026-80255
GCVE (VulDB): GCVE-100-399473
EUVD: 🔒

Entryinfo

Created: 09/06/2026 20:10
Updated: 09/06/2026 21:45
Changes: 09/06/2026 20:10 (52), 09/06/2026 21:45 (1)
Complete: 🔍
Cache ID: 216::103

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.