Security readout for executives and security teams
Plain-English summary
CVE-2020-1045 is a security feature bypass in Microsoft ASP.NET Core cookie parsing. An attacker could exploit percent-encoded cookie names to create a second cookie that the application may interpret incorrectly. The main business risk is unauthorized manipulation of application state or security decisions, not data theft or service outage.
Executive priority
Treat this as a high-priority patching item for exposed ASP.NET Core applications. The risk is integrity compromise through security bypass, with remote unauthenticated reach, but available evidence does not confirm active exploitation.
Technical view
ASP.NET Core decoded entire cookie strings instead of safely handling encoded cookie names. This could allow duplicate logical cookie names, including one percent encoded, leading to integrity-impacting security bypass. The CVSS 3.1 score is 7.5, with network attack vector, low complexity, no privileges, no user interaction, and high integrity impact.
Likely exposure
Exposure is most likely in applications running affected ASP.NET Core 2.1 or 3.1 components that accept browser or API cookies from untrusted clients. Internet-facing apps, authentication flows, session handling, and middleware relying on cookie names deserve priority review.
Exploitation context
The source bundle does not show CISA KEV listing or confirmed active exploitation. The CVSS vector includes proof-of-concept exploit maturity, but no cited source here confirms active in-the-wild exploitation.
Researcher notes
Focus analysis on cookie-name canonicalization and middleware assumptions around duplicate or encoded cookie names. Do not assume confidentiality or availability impact from the provided CVSS; the stated impact is integrity high, confidentiality none, availability none.
Mitigation direction
- Apply Microsoft security updates for affected ASP.NET Core versions.
- Update Fedora or Red Hat .NET packages using the cited vendor advisories.
- Inventory containers, hosts, and build images for affected ASP.NET Core runtimes.
- Check MSRC and vendor advisories for exact fixed package versions.
- Regression test authentication and session flows after updating.
Validation and detection
- Identify ASP.NET Core runtime and package versions across production assets.
- Check dependency manifests, container images, and host runtimes for affected versions.
- Confirm installed packages match Microsoft, Fedora, or Red Hat fixed releases.
- Review internet-facing apps that depend on cookie-based security decisions.
- Verify cookie parsing behavior through safe regression tests only.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CVE-2020-1045 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 7.5 (3.1)
- Known Exploited
- No
- Published
Vector: 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
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N/E:P/RL:O/RC:C3.93.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: 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
Source materials
- CVE List V5 sourceCVE List V5
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-1045CVE reference
- FEDORA-2020-e2deb72e0fCVE reference · vendor-advisory
- FEDORA-2020-48fa1ad65cCVE reference · vendor-advisory
- https://github.com/dotnet/core/blob/main/release-notes/3.1/3.1.8/3.1.8.md#changes-in-318CVE reference
- https://security.snyk.io/vuln/SNYK-RHEL8-DOTNET-1439600CVE reference
- https://access.redhat.com/errata/RHSA-2020:3699CVE reference
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.