CVE-2020-1045
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Microsoft ASP.NET Core Security Feature Bypass Vulnerability
rank 24 = 1 + 13 + 1 + 9 + 0
rank@v1 · backlog
Someone is already using it
CISA KEV catalog · public proof-of-concept · FIRST EPSS
EPSS 0.05926 · without this subject the record ranks 23
What it costs you if it fires
NVD CVSS base score, then the CNA's own
CVSS 5.0, from NVD · without this subject the record ranks 11
It is getting worse, not staying still
FIRST EPSS series, rescorings and bad loads removed
rose on 2025-09-24 · without this subject the record ranks 23
How much of the world it touches
NVD CPE configurations
14 products in the CPE ranges · without this subject the record ranks 15
Someone else already set the date
CISA KEV remediation due date
no CISA due date · without this subject the record ranks 24
$181,000 = $4.99M incident cost x 0.6121449559255632 exposure x 0.05926 likelihood
udv@v1 · unaudited · wrong for you until you say what you run
$4.99M is the cost of a breach that happened, from IBM Cost of a Data Breach Report 2026, global average. It is not the value of any asset of yours. That average already covers breaches of every severity, so scaling it by exposure understates a partial-impact record. That is an assumption, not a measurement. Your own asset value goes in the decision record.
Hindsight · the state
Foresight · where to check next
No weakness class or product neighbourhood is held for this record, so this index cannot name anywhere to check next. That is an absence in the record, not a finding about the software.
Sources disagree here.
Both shown, dated. We don't pick winners. disagreement-rules@v1
Running Microsoft ASP.NET Core 2.1? Check your version
A deterministic range check against the ranges this record publishes. It tells you where a version sits in the record, not whether your deployment is exploitable. No account needed.
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Harm, if it fires from the vector and the weakness
Written for the ticket you're about to file.
CISA KEV & Federal Remediation Deadline from the record and CISA
The fix, and how long it's been waiting.
Exploit Status & Known PoCs a ladder, not a score
Current rung: Nothing observed in held sources.
- RUNG 1Nothing observed in held sources
- RUNG 2Proof-of-concept published
- RUNG 3Exploited in the wild · CISA KEV listed
- RUNG 4Ransomware campaign use known
Affected & Fixed Versions as published
Show all 14 published ranges
A rung lights from a row in the index, never from an assessment. "Held sources" is the true scope of the claim: this index reads the CVE record, NVD, CISA KEV, FIRST's EPSS and public proof-of-concept repositories, and it does not observe attacks.
What it is stated by the CNA
<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> receipt
NVD's analysis a second authority
- severity
- 5 AV:N/AC:L/Au:N/C:N/I:P/A:N
- affected versions
- microsoft asp.net core >= 2.1 <= 2.1.21; microsoft asp.net core >= 3.1 < 3.1.8; fedoraproject fedora 32; and 11 more, listed in full below
- also scored by
- [email protected] 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N · [email protected] 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
The CNA scored it 7.5 and NVD 5. Both are shown because both were published; we do not pick one.
check it yourself portal.msrc.microsoft.com lists.fedoraproject.org lists.fedoraproject.org github.com security.snyk.io access.redhat.com receipt
Dated events
Movement the material steps
This score more than doubled inside 72 hours. Both observations are in the full history below.
Show all 35 observations
35 observations held. A highlighted step crossed a promotion threshold. A step marked with a scoring model moved because the instrument was replaced, not because the vulnerability changed. receipt
The full biography
Exploit probability more than doubled between 2025-11-18 and 2025-11-21 (0.08102 → 0.20523) and the record had been public for 6 years when this index was last written.
Siblings and hubs
Records related to this one
None. No alias set, and nothing in the corpus cites this identifier or shares its product family within 60 days.
Browse the index from here
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What usually comes next
Everything above needs no account. What is below is work: assembling it, scoping it to your estate, watching it, and handing it to someone else.