Vulnerability Monitor

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CVE-2020-1045

A security feature bypass vulnerability exists in the way Microsoft ASP.NET Core parses encoded cookie names. The ASP.NET Core cookie parser decodes entire cookie strings which could allow a malicious attacker to set a second cookie with the name being percent encoded. The security update addresses the vulnerability by fixing the way the ASP.NET Core cookie parser handles encoded names.

Security Impact Summary

This vulnerability carries a HIGH severity rating with a CVSS v3.1 score of 7.5, indicating it can be exploited remotely over the network with relatively low complexity without requiring user interaction and does not require pre-existing privileges . The vulnerability impacts integrity (unauthorized modifications), for affected systems. Impacting 6 products from microsoft, from fedoraproject, from redhat and 3 others, organizations running these solutions should prioritize assessment and patching.

Historical Context

Reported in 2020, this vulnerability emerged during an era marked by increased sophistication in supply chain attacks, cloud infrastructure vulnerabilities, and software-as-a-service (SaaS) security challenges. Security practices during this period emphasized zero-trust architectures, container security, and API protection.

Published

2020-09-11T17:15:18.307

Last Modified

2026-06-17T03:00:18.787

Status

Modified

Source

[email protected]

Severity

CVSSv3.1: 7.5 (HIGH)

CVSSv2 Vector

AV:N/AC:L/Au:N/C:N/I:P/A:N

Access Vector: NETWORK
Access Complexity: LOW
Authentication: NONE
Confidentiality Impact: NONE
Integrity Impact: PARTIAL
Availability Impact: NONE

Exploitability Score

10.0

Impact Score

2.9

Weaknesses

Type: Primary
NVD-CWE-noinfo

Affected Vendors & Products

Type	Vendor	Product	Version/Range	Vulnerable?
Application	microsoft	asp.net_core	≤ 2.1.21	Yes
Application	microsoft	asp.net_core	< 3.1.8	Yes
Operating System	fedoraproject	fedora	32	Yes
Operating System	fedoraproject	fedora	33	Yes
Operating System	redhat	enterprise_linux	8.0	Yes
Operating System	redhat	enterprise_linux_aus	8.2	Yes
Operating System	redhat	enterprise_linux_aus	8.4	Yes
Operating System	redhat	enterprise_linux_aus	8.6	Yes
Operating System	redhat	enterprise_linux_eus	8.2	Yes
Operating System	redhat	enterprise_linux_eus	8.4	Yes
Operating System	redhat	enterprise_linux_eus	8.6	Yes
Operating System	redhat	enterprise_linux_tus	8.2	Yes
Operating System	redhat	enterprise_linux_tus	8.4	Yes
Operating System	redhat	enterprise_linux_tus	8.6	Yes

References

https://access.redhat.com/errata/RHSA-2020:3699 Third Party Advisory ([email protected])
https://github.com/dotnet/core/blob/main/release-notes/3.1/3.1.8/3.1.8.md#changes-in-318 Release Notes, Third Party Advisory ([email protected])
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/5LN2FUVBSVPGK7AU3NMLO3YR6CGONQPB/ ([email protected])
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ASICXQXS4M7MTAF6SGQMCLCA63DLCUT3/ ([email protected])
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-1045 Patch, Vendor Advisory ([email protected])
https://security.snyk.io/vuln/SNYK-RHEL8-DOTNET-1439600 Third Party Advisory ([email protected])
https://access.redhat.com/errata/RHSA-2020:3699 Third Party Advisory (af854a3a-2127-422b-91ae-364da2661108)
https://github.com/dotnet/core/blob/main/release-notes/3.1/3.1.8/3.1.8.md#changes-in-318 Release Notes, Third Party Advisory (af854a3a-2127-422b-91ae-364da2661108)
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/5LN2FUVBSVPGK7AU3NMLO3YR6CGONQPB/ (af854a3a-2127-422b-91ae-364da2661108)
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ASICXQXS4M7MTAF6SGQMCLCA63DLCUT3/ (af854a3a-2127-422b-91ae-364da2661108)
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-1045 Patch, Vendor Advisory (af854a3a-2127-422b-91ae-364da2661108)
https://security.snyk.io/vuln/SNYK-RHEL8-DOTNET-1439600 Third Party Advisory (af854a3a-2127-422b-91ae-364da2661108)

How SecUtils Interprets This CVE

SecUtils normalizes and enriches National Vulnerability Database (NVD) records by standardizing vendor and product identifiers, aggregating vulnerability metadata from both NVD and MITRE sources, and providing structured context for security teams. For microsoft's affected products, we extract Common Platform Enumeration (CPE) data, Common Weakness Enumeration (CWE) classifications, CVSS severity metrics, and reference data to enable rapid vulnerability prioritization and asset correlation. This record contains no exploit code, proof-of-concept instructions, or attack methodologies—only defensive intelligence necessary for patch management, risk assessment, and security operations.