CVE-2020-1045Microsoft ASP.NET Core Security Feature Bypass Vulnerability
- 7.5HighCVSS base score
- 5.9%Exploitation in 30 daysEPSS · top 6.6% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
<p>A security feature bypass vulnerability exists in the way Microsoft ASP.NET Core parses encoded cookie names.</p> <p>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.</p> <p>The security update addresses the vulnerability by fixing the way the ASP.NET Core cookie parser handles encoded names.</p>
Timeline
ID reserved
By microsoft
- 10 months later
· 10 months later
Published
- 4 years later
· 4 years later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| microsoftCNA (assigner) | 3.1 | High7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N/E:P/RL:O/RC:C |
| NVDNVD · Modified | 3.1 | High7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N |
- EPSS (exploitation in 30 days)
- 5.9% · top 6.6% of all CVEs (12 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: yes · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.5.
Affected products
- affected 2.0 – < publication
- affected 3.0 – < publication
Affected packages
Affected packages13
From reviewed advisories of the GitHub Advisory Database.
- NuGetMicrosoft.AspNetCore.AppGHSA-hxrm-9w7p-39cc (opens in a new tab)
- NuGetMicrosoft.AspNetCore.App.Runtime.linux-armGHSA-hxrm-9w7p-39cc (opens in a new tab)
- NuGetMicrosoft.AspNetCore.App.Runtime.linux-arm64GHSA-hxrm-9w7p-39cc (opens in a new tab)
- NuGetMicrosoft.AspNetCore.App.Runtime.linux-musl-arm64GHSA-hxrm-9w7p-39cc (opens in a new tab)
- NuGetMicrosoft.AspNetCore.App.Runtime.linux-musl-x64GHSA-hxrm-9w7p-39cc (opens in a new tab)
- NuGetMicrosoft.AspNetCore.App.Runtime.linux-x64GHSA-hxrm-9w7p-39cc (opens in a new tab)
- NuGetMicrosoft.AspNetCore.App.Runtime.osx-x64GHSA-hxrm-9w7p-39cc (opens in a new tab)
- NuGetMicrosoft.AspNetCore.App.Runtime.win-armGHSA-hxrm-9w7p-39cc (opens in a new tab)
- NuGetMicrosoft.AspNetCore.App.Runtime.win-arm64GHSA-hxrm-9w7p-39cc (opens in a new tab)
- NuGetMicrosoft.AspNetCore.App.Runtime.win-x64GHSA-hxrm-9w7p-39cc (opens in a new tab)
- NuGetMicrosoft.AspNetCore.App.Runtime.win-x86GHSA-hxrm-9w7p-39cc (opens in a new tab)
- NuGetMicrosoft.AspNetCore.HttpGHSA-hxrm-9w7p-39cc (opens in a new tab)
- NuGetMicrosoft.OwinGHSA-hxrm-9w7p-39cc (opens in a new tab)
References
References6
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-1045 (opens in a new tab)x_transferred
- FEDORA-2020-e2deb72e0f (opens in a new tab)vendor-advisoryx_transferred
- FEDORA-2020-48fa1ad65c (opens in a new tab)vendor-advisoryx_transferred
- https://github.com/dotnet/core/blob/main/release-notes/3.1/3.1.8/3.1.8.md#changes-in-318 (opens in a new tab)x_transferred
- https://security.snyk.io/vuln/SNYK-RHEL8-DOTNET-1439600 (opens in a new tab)x_transferred
- https://access.redhat.com/errata/RHSA-2020:3699 (opens in a new tab)x_transferred
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2022-4249 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-hxrm-9w7p-39cc (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2020-1045)Record last updated .