CVE-2026-40372: Improper verification of cryptographic signature in ASP.NET Core allows an unauthorized attacker to elevate pr

This week

CRITICAL 9.1REMOTEWATCHLISTUPGRADE

CVE-2026-40372 is a critical-severity flaw (CVSS 9.1) affecting asp.net core. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Improper verification of cryptographic signature in ASP.NET Core allows an unauthorized attacker to elevate privileges over a network.

Why this priority

Critical severity
EPSS top 4%: very likely to be exploited
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	9.1 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	11.2% (top 4%)
CISA exploited list	No
Weakness	CWE-347
Published	2026-04-21
Last modified	2026-10-26

Publisher (CNA): Microsoft Corporation · Vendor: microsoft

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-21 20:16 UTCPublished CVE record published
2026-10-26 21:10 UTCUpdated Record last modified

microsoft asp.net core UPGRADE

Affected: >= 10.0.0 and < 10.0.7

Fixed in: 10.0.7

Safe to downgrade to: a release before 10.0.0

1. Check installed version

apt-cache policy asp.net-core || rpm -q asp.net-core || asp.net-core --version

2. UPGRADE to 10.0.7 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade asp.net-core

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade asp.net-core

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 10.0.0 (Debian / Ubuntu)

apt-cache madison asp.net-core sudo apt install asp.net-core=<VERSION_BEFORE_10.0.0> sudo apt-mark hold asp.net-core

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list asp.net-core sudo dnf downgrade asp.net-core-<VERSION_BEFORE_10.0.0> sudo dnf versionlock add asp.net-core

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-40372?

asp.net core: upgrade to 10.0.7. Exact commands for each OS are on this page.

Is CVE-2026-40372 being exploited?

CVE-2026-40372 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-40372 affect?

CVE-2026-40372 affects asp.net core. Severity is critical (CVSS 9.1). Improper verification of cryptographic signature in ASP.NET Core allows an unauthorized attacker to elevate privileges over a network.

How urgent is CVE-2026-40372?

Priority 66/100. Critical severity; EPSS top 4%: very likely to be exploited; Remotely exploitable, no login, no user action; On your watchlist

Software pages

.NET vulnerabilities

Related CVEs

CVE-2026-88092 CRITICAL 9.4 UPGRADE UPGRADE Inconsistent interpretation of http requests ('http request/response smuggling') in ASP.NET Core allows an una
CVE-2026-69304 MEDIUM 5.9 UPGRADE UPGRADE Improper handling of highly compressed data (data amplification) in ASP.NET Core allows an unauthorized attack

References

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