CVE-2026-58649: Origin validation error in .NET allows an unauthorized attacker to disclose information over a network.

Routine

MEDIUM 6.5WATCHLISTDOWNGRADEUPGRADEUPGRADE

CVE-2026-58649 is a medium-severity flaw (CVSS 6.5) affecting .net, .net sdk, visual studio 2022. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Origin validation error in .NET allows an unauthorized attacker to disclose information over a network.

Why this priority

On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.4% (top 71%)
CISA exploited list	No
Weakness	CWE-346
Published	2026-09-08
Last modified	2026-10-07

Publisher (CNA): Microsoft Corporation · Vendor: microsoft

Last updated 2026-10-07 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-09-08 18:17 UTCPublished CVE record published
2026-10-07 15:05 UTCUpdated Record last modified

microsoft .net DOWNGRADE

Affected: 11.0.0 preview1 · 11.0.0 preview2 · 11.0.0 preview3 · 11.0.0 preview4 · 11.0.0 preview5 · 11.0.0 preview6 · 11.0.0 preview7

Fixed in: no fixed release known

Safe to downgrade to: a release before 11.0.0

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 11.0.0 (Debian / Ubuntu)

apt-cache madison .net sudo apt install .net=<VERSION_BEFORE_11.0.0> sudo apt-mark hold .net

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list .net sudo dnf downgrade .net-<VERSION_BEFORE_11.0.0> sudo dnf versionlock add .net

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.

microsoft .net sdk UPGRADE

Affected: >= 8.0.100 and < 8.0.130 · >= 8.0.200 and < 8.0.424 · >= 9.0.100 and < 9.0.120 · >= 9.0.200 and < 9.0.317 · >= 10.0.100 and < 10.0.111 · >= 10.0.200 and < 10.0.400

Fixed in: 8.0.130, 8.0.424, 9.0.120, 9.0.317, 10.0.111, 10.0.400

Safe to downgrade to: a release before 8.0.100

1. Check installed version

apt-cache policy .net-sdk || rpm -q .net-sdk || .net-sdk --version

2. UPGRADE to 8.0.130 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade .net-sdk

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade .net-sdk

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 8.0.100 (Debian / Ubuntu)

apt-cache madison .net-sdk sudo apt install .net-sdk=<VERSION_BEFORE_8.0.100> sudo apt-mark hold .net-sdk

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

dnf --showduplicates list .net-sdk sudo dnf downgrade .net-sdk-<VERSION_BEFORE_8.0.100> sudo dnf versionlock add .net-sdk

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.

microsoft visual studio 2022 UPGRADE

Affected: >= 17.14.0 and < 17.14.40

Fixed in: 17.14.40

Safe to downgrade to: a release before 17.14.0

1. Check installed version

apt-cache policy visual-studio-2022 || rpm -q visual-studio-2022 || visual-studio-2022 --version

2. UPGRADE to 17.14.40 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade visual-studio-2022

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade visual-studio-2022

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 17.14.0 (Debian / Ubuntu)

apt-cache madison visual-studio-2022 sudo apt install visual-studio-2022=<VERSION_BEFORE_17.14.0> sudo apt-mark hold visual-studio-2022

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

dnf --showduplicates list visual-studio-2022 sudo dnf downgrade visual-studio-2022-<VERSION_BEFORE_17.14.0> sudo dnf versionlock add visual-studio-2022

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.

microsoft visual studio 2026 UPGRADE

Affected: >= 18.9.0 and < 18.9.3

Fixed in: 18.9.3

Safe to downgrade to: a release before 18.9.0

1. Check installed version

apt-cache policy visual-studio-2026 || rpm -q visual-studio-2026 || visual-studio-2026 --version

2. UPGRADE to 18.9.3 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade visual-studio-2026

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade visual-studio-2026

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 18.9.0 (Debian / Ubuntu)

apt-cache madison visual-studio-2026 sudo apt install visual-studio-2026=<VERSION_BEFORE_18.9.0> sudo apt-mark hold visual-studio-2026

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

dnf --showduplicates list visual-studio-2026 sudo dnf downgrade visual-studio-2026-<VERSION_BEFORE_18.9.0> sudo dnf versionlock add visual-studio-2026

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-2026-58649?

.net: downgrade or apply the listed mitigation; .net sdk: upgrade to 8.0.130, 8.0.424, 9.0.120, 9.0.317, 10.0.111, 10.0.400; visual studio 2022: upgrade to 17.14.40. Exact commands for each OS are on this page.

Is CVE-2026-58649 being exploited?

CVE-2026-58649 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-2026-58649 affect?

CVE-2026-58649 affects .net, .net sdk, visual studio 2022. Severity is medium (CVSS 6.5). Origin validation error in .NET allows an unauthorized attacker to disclose information over a network.

How urgent is CVE-2026-58649?

Priority 35/100. On your watchlist

Software pages

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References

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