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No exploitation reportedFix available

CVE-2020-1045

No exploitation reported by the sources we read.

  • Published2020-09-11
  • Fixed in3.1.8

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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

dates in UTC
  1. 2020-09-1117:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2020-1045?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2020-1045?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD · OSV
ASP.NET Core
BranchAffectedFixed in
3.1≥ 3.1, < 3.1.83.1.8
3.1≥ 3.1.0, < 3.1.83.1.8
3.1≥ 3.1.5, < 3.1.83.1.8
2.1≥ 2.1, ≤ 2.1.21no fix published
Redhat enterprise linux aus
BranchAffectedFixed in
8.2= 8.2no fix published
8.4= 8.4no fix published
8.6= 8.6no fix published
Redhat enterprise linux eus
BranchAffectedFixed in
8.2= 8.2no fix published
8.4= 8.4no fix published
8.6= 8.6no fix published

6 more products in the sources.

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

  1. Update ASP.NET Core to 3.1.8

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub

Sources

  • CISA-ADPSSVC decisionnone2024-01-10
  • OpenCVESSVC decisionnone—
  • CNACVSS 3.17.5read 2026-10-23
  • NVDCVSS 3.17.5read 2026-10-23
  • NVDCVSS 2.05read 2026-10-23
  • FIRST EPSSEPSS score5.9 %2026-10-23
  • OSVaffected packages—

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Published
2020-09-11
Last Modified
2026-06-17
NVD status
Modified

Frequently asked questions

What is CVE-2020-1045?

<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>

Is CVE-2020-1045 actively exploited?

Active exploitation of CVE-2020-1045 has not been confirmed. Its EPSS score was 5.9% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2020-1045?

CVE-2020-1045 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.

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