Skip to content
Noroxi
NVD / CVE Program· CNA microsoft

CVE-2020-1045: Microsoft ASP.NET Core Security Feature Bypass Vulnerability

Noroxi assessment

Priority: Monitor (action score 32/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 5.9% (FIRST EPSS); higher than 93.1% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • According to CISA the attack is automatable: targets can be found by mass scanning.
  • Fixed version: Microsoft.AspNetCore.App (NuGet) 2.1.22; Microsoft.AspNetCore.App.Runtime.linux-arm (NuGet) 3.1.8; Microsoft.AspNetCore.App.Runtime.linux-arm64 (NuGet) 3.1.8.

Low priority for now. Upgrade to Microsoft.AspNetCore.App (NuGet) 2.1.22; Microsoft.AspNetCore.App.Runtime.linux-arm (NuGet) 3.1.8; Microsoft.AspNetCore.App.Runtime.linux-arm64 (NuGet) 3.1.8 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

<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>

HighCVSS 7.5 · v3.1—No exploit Fix available
Published
Sep 11, 2020
Updated
Jun 16, 2026
EPSS
5.9% · 93th percentile
CWE
—

Report tools

JSON

Action score

32

Monitor

Low priority for now.

CVSS
30 / 40 · 7.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
2 / 30 · 5.9%

CISA SSVC decision

Exploitation
none
Automatable
yes
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · microsoft
7.5
NVD has not scored this yet; the score shown is the CNA’s.

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2020-1045

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

One daily email digest (06:00 UTC); connect a webhook for KEV listings and weaponized exploits instantly.

Your free account also gets you

Running WordPress? Scan your site free with WP Lens

  • Stack alerts: add the products and versions you run, get the new CVEs that affect them
  • Uptime monitoring: 1 site, instant email when it goes down
  • Add your domain: subdomains and takeover risk scanned every week (1 domain)
  • 10 scans an hour on the security tools (3 a day without an account), an API key and MCP
  • All your scans in one panel: findings, what changed in the last scan, a report per domain or per client (PDF, share link)
All free tools

Sign up with email · Have an account? Sign in

Free account, no card. Unfollow any time.

Don't want an account? Get "Exploited this week" by email every MondayDon't want an account? RSS feed for microsoft records

Running WordPress? Scan your site free with WP Lens

Is your version affected? Check it

Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

We use this product, ask for help

Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
microsoftasp.net core
fedoraprojectfedora
redhatenterprise linux
redhatenterprise linux aus
redhatenterprise linux eus
redhatenterprise linux tus

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • fedoraproject fedora32
  • fedoraproject fedora33
  • microsoft asp.net core3.1 and later · before 3.1.8
  • microsoft asp.net core2.1 and later · up to 2.1.21 inclusive
  • redhat enterprise linux8.0
  • redhat enterprise linux aus8.2
  • redhat enterprise linux aus8.4
  • redhat enterprise linux aus8.6
  • redhat enterprise linux eus8.2
  • redhat enterprise linux eus8.4
  • redhat enterprise linux eus8.6
  • redhat enterprise linux tus8.2
  • redhat enterprise linux tus8.4
  • redhat enterprise linux tus8.6

Versions reported by the vendor

Affected version ranges reported by the assigning authority (microsoft). Independent of NVD's CPE analysis and usually ahead of it.

  • Microsoft ASP.NET Core 2.1

    • 2.0 and later · before publicationaffected

  • Microsoft ASP.NET Core 3.1

    • 3.0 and later · before publicationaffected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
NuGetMicrosoft.AspNetCore.Appbefore 2.1.222.1.22
NuGetMicrosoft.AspNetCore.App.Runtime.linux-armfrom 3.1.0 · before 3.1.83.1.8
NuGetMicrosoft.AspNetCore.App.Runtime.linux-arm64from 3.1.0 · before 3.1.83.1.8
NuGetMicrosoft.AspNetCore.App.Runtime.linux-musl-arm64from 3.1.0 · before 3.1.83.1.8
NuGetMicrosoft.AspNetCore.App.Runtime.linux-musl-x64from 3.1.0 · before 3.1.83.1.8
NuGetMicrosoft.AspNetCore.App.Runtime.linux-x64from 3.1.0 · before 3.1.83.1.8
NuGetMicrosoft.AspNetCore.App.Runtime.osx-x64from 3.1.0 · before 3.1.83.1.8
NuGetMicrosoft.AspNetCore.App.Runtime.win-armfrom 3.1.0 · before 3.1.83.1.8
NuGetMicrosoft.AspNetCore.App.Runtime.win-arm64from 3.1.5 · before 3.1.83.1.8
NuGetMicrosoft.AspNetCore.App.Runtime.win-x64from 3.1.0 · before 3.1.83.1.8
NuGetMicrosoft.AspNetCore.App.Runtime.win-x86from 3.1.0 · before 3.1.83.1.8
NuGetMicrosoft.AspNetCore.Httpbefore 2.1.222.1.22
NuGetMicrosoft.Owinbefore 4.1.14.1.1
Red Hat:enterprise_linux:8::appstreamaspnetcore-runtime-3.1before 0:3.1.8-2.el8_20:3.1.8-2.el8_2
Red Hat:enterprise_linux:8::appstreamaspnetcore-targeting-pack-3.1before 0:3.1.8-2.el8_20:3.1.8-2.el8_2
Red Hat:enterprise_linux:8::appstreamdotnetbefore 0:3.1.108-2.el8_20:3.1.108-2.el8_2
Red Hat:enterprise_linux:8::appstreamdotnet-apphost-pack-3.1before 0:3.1.8-2.el8_20:3.1.8-2.el8_2
Red Hat:enterprise_linux:8::appstreamdotnet-apphost-pack-3.1-debuginfobefore 0:3.1.8-2.el8_20:3.1.8-2.el8_2
Red Hat:enterprise_linux:8::appstreamdotnet-hostbefore 0:3.1.8-2.el8_20:3.1.8-2.el8_2
Red Hat:enterprise_linux:8::appstreamdotnet-host-debuginfobefore 0:3.1.8-2.el8_20:3.1.8-2.el8_2
Red Hat:enterprise_linux:8::appstreamdotnet-hostfxr-3.1before 0:3.1.8-2.el8_20:3.1.8-2.el8_2
Red Hat:enterprise_linux:8::appstreamdotnet-hostfxr-3.1-debuginfobefore 0:3.1.8-2.el8_20:3.1.8-2.el8_2
Red Hat:enterprise_linux:8::appstreamdotnet-runtime-3.1before 0:3.1.8-2.el8_20:3.1.8-2.el8_2
Red Hat:enterprise_linux:8::appstreamdotnet-runtime-3.1-debuginfobefore 0:3.1.8-2.el8_20:3.1.8-2.el8_2

+20

Same product

microsoft: all records

Other highest-scoring records for the same primary product.

  • CVE-2025-55315ASP.NET Security Feature Bypass Vulnerability
    59Plan
  • CVE-2020-0603A remote code execution vulnerability exists in ASP.NET Core software when the software fails to handle objects in memory.An attacker who su
    41Plan
  • CVE-2026-40372ASP.NET Core Elevation of Privilege Vulnerability
    39Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2020-1161May 21, 2020 · ASP.NET Core Denial of Service Vulnerability
    32Monitor
  • ← EarlierCVE-2020-1597Aug 17, 2020 · ASP.NET Core Denial of Service Vulnerability
    32Monitor
  • Later →CVE-2021-1723Jan 12, 2021 · ASP.NET Core and Visual Studio Denial of Service Vulnerability
    32Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
NuGet:Microsoft.AspNetCore.App2.1.22Package registry (OSV)
NuGet:Microsoft.AspNetCore.App.Runtime.linux-arm3.1.8Package registry (OSV)
NuGet:Microsoft.AspNetCore.App.Runtime.linux-arm643.1.8Package registry (OSV)
NuGet:Microsoft.AspNetCore.App.Runtime.linux-musl-arm643.1.8Package registry (OSV)
NuGet:Microsoft.AspNetCore.App.Runtime.linux-musl-x643.1.8Package registry (OSV)
NuGet:Microsoft.AspNetCore.App.Runtime.linux-x643.1.8Package registry (OSV)
NuGet:Microsoft.AspNetCore.App.Runtime.osx-x643.1.8Package registry (OSV)
NuGet:Microsoft.AspNetCore.App.Runtime.win-arm3.1.8Package registry (OSV)
NuGet:Microsoft.AspNetCore.App.Runtime.win-arm643.1.8Package registry (OSV)
NuGet:Microsoft.AspNetCore.App.Runtime.win-x643.1.8Package registry (OSV)
NuGet:Microsoft.AspNetCore.App.Runtime.win-x863.1.8Package registry (OSV)
NuGet:Microsoft.AspNetCore.Http2.1.22Package registry (OSV)
NuGet:Microsoft.Owin4.1.1Package registry (OSV)
red hat:rh-dotnet31-aspnetcore-runtime-3.10:3.1.8-1.el7 · Red Hat:rhel_dotnet:3.1::el7Package registry (OSV)
red hat:rh-dotnet31-aspnetcore-targeting-pack-3.10:3.1.8-1.el7 · Red Hat:rhel_dotnet:3.1::el7Package registry (OSV)
red hat:rh-dotnet31-dotnet0:3.1.108-1.el7 · Red Hat:rhel_dotnet:3.1::el7Package registry (OSV)
red hat:rh-dotnet31-dotnet-apphost-pack-3.10:3.1.8-1.el7 · Red Hat:rhel_dotnet:3.1::el7Package registry (OSV)
red hat:rh-dotnet31-dotnet-debuginfo0:3.1.108-1.el7 · Red Hat:rhel_dotnet:3.1::el7Package registry (OSV)
red hat:rh-dotnet31-dotnet-host0:3.1.8-1.el7 · Red Hat:rhel_dotnet:3.1::el7Package registry (OSV)
red hat:rh-dotnet31-dotnet-hostfxr-3.10:3.1.8-1.el7 · Red Hat:rhel_dotnet:3.1::el7Package registry (OSV)
red hat:rh-dotnet31-dotnet-runtime-3.10:3.1.8-1.el7 · Red Hat:rhel_dotnet:3.1::el7Package registry (OSV)
red hat:rh-dotnet31-dotnet-sdk-3.10:3.1.108-1.el7 · Red Hat:rhel_dotnet:3.1::el7Package registry (OSV)
red hat:rh-dotnet31-dotnet-targeting-pack-3.10:3.1.8-1.el7 · Red Hat:rhel_dotnet:3.1::el7Package registry (OSV)
red hat:rh-dotnet31-dotnet-templates-3.10:3.1.108-1.el7 · Red Hat:rhel_dotnet:3.1::el7Package registry (OSV)
red hat:rh-dotnet31-netstandard-targeting-pack-2.10:3.1.108-1.el7 · Red Hat:rhel_dotnet:3.1::el7Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days-1% in 7 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
high · data or configuration can be modified
Availability
none
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
High
Availability impact
None

Weakness class (CWE)

—

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (5 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records