CVE-2026-26127: Out-of-bounds read in .NET allows an unauthorized attacker to deny service over a network.

Q: How do I fix CVE-2026-26127?

.net: upgrade to 9.0.14, 10.0.4; bcl.memory: upgrade to 9.0.14, 10.0.4. Exact commands for each OS are on this page.

Q: Is CVE-2026-26127 being exploited?

CVE-2026-26127 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-26127 affect?

CVE-2026-26127 affects .net, bcl.memory. Severity is high (CVSS 7.5). Out-of-bounds read in .NET allows an unauthorized attacker to deny service over a network.

Q: How urgent is CVE-2026-26127?

Priority 57/100. High severity; Remotely exploitable, no login, no user action; On your watchlist

This month

HIGH 7.5REMOTEWATCHLISTUPGRADEUPGRADE

CVE-2026-26127 is a high-severity flaw (CVSS 7.5) affecting .net, bcl.memory. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Out-of-bounds read in .NET allows an unauthorized attacker to deny service over a network.

Why this priority

High severity
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	2.1% (top 18%)
CISA exploited list	No
Weakness	CWE-125
Published	2026-03-10
Last modified	2026-06-17

Publisher (CNA): Microsoft Corporation · Vendor: microsoft

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-03-10 18:18 UTCPublished CVE record published
2026-06-17 10:25 UTCUpdated Record last modified

microsoft .net UPGRADE

Affected: >= 10.0.0 and < 10.0.4 · >= 9.0.0 and < 9.0.14

Fixed in: 9.0.14, 10.0.4

Safe to downgrade to: a release before 9.0.0

1. Check installed version

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

2. UPGRADE to 9.0.14 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade .net

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 9.0.0 (Debian / Ubuntu)

apt-cache madison .net sudo apt install .net=<VERSION_BEFORE_9.0.0> sudo apt-mark hold .net

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

dnf --showduplicates list .net sudo dnf downgrade .net-<VERSION_BEFORE_9.0.0> 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 bcl.memory UPGRADE

Affected: >= 9.0.0 and < 9.0.14 · >= 10.0.0 and < 10.0.4

Fixed in: 9.0.14, 10.0.4

Safe to downgrade to: a release before 9.0.0

1. Check installed version

apt-cache policy bcl.memory || rpm -q bcl.memory || bcl.memory --version

2. UPGRADE to 9.0.14 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade bcl.memory

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade bcl.memory

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 9.0.0 (Debian / Ubuntu)

apt-cache madison bcl.memory sudo apt install bcl.memory=<VERSION_BEFORE_9.0.0> sudo apt-mark hold bcl.memory

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

dnf --showduplicates list bcl.memory sudo dnf downgrade bcl.memory-<VERSION_BEFORE_9.0.0> sudo dnf versionlock add bcl.memory

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.

Exact fixes by distribution

NuGet (.NET) · Microsoft.Bcl.Memory · FIXED · 9.0.14 · vulnerable: >= 9.0.0, <= 9.0.13 · source

dotnet add package Microsoft.Bcl.Memory --version 9.0.14

NuGet (.NET) · Microsoft.NetCore.App.Runtime.linux-arm · FIXED · 9.0.14 · vulnerable: >= 9.0.0, <= 9.0.13 · source

dotnet add package Microsoft.NetCore.App.Runtime.linux-arm --version 9.0.14

NuGet (.NET) · Microsoft.NetCore.App.Runtime.linux-arm64 · FIXED · 9.0.14 · vulnerable: >= 9.0.0, <= 9.0.13 · source

dotnet add package Microsoft.NetCore.App.Runtime.linux-arm64 --version 9.0.14

NuGet (.NET) · Microsoft.NetCore.App.Runtime.linux-musl-arm · FIXED · 9.0.14 · vulnerable: >= 9.0.0, <= 9.0.13 · source

dotnet add package Microsoft.NetCore.App.Runtime.linux-musl-arm --version 9.0.14

NuGet (.NET) · Microsoft.NetCore.App.Runtime.linux-musl-arm64 · FIXED · 9.0.14 · vulnerable: >= 9.0.0, <= 9.0.13 · source

dotnet add package Microsoft.NetCore.App.Runtime.linux-musl-arm64 --version 9.0.14

NuGet (.NET) · Microsoft.NetCore.App.Runtime.linux-musl-x64 · FIXED · 9.0.14 · vulnerable: >= 9.0.0, <= 9.0.13 · source

dotnet add package Microsoft.NetCore.App.Runtime.linux-musl-x64 --version 9.0.14

Fedora ELN · intel-ipsec-mb · FIXED · 3.0.1-1.eln159 · FEDORA-2026-ca01077210 · source

sudo dnf upgrade --advisory=FEDORA-2026-ca01077210

Fedora 46 · complytime-providers · FIXED · 0.3.0-2.fc46 · FEDORA-2026-7c372be466 · source

sudo dnf upgrade --advisory=FEDORA-2026-7c372be466

Ubuntu 24.04 · dotnet10 · FIXED · 10.0.104-10.0.4-0ubuntu1~24.04.1

sudo apt update && sudo apt install --only-upgrade dotnet10 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' dotnet10)" ge "10.0.104-10.0.4-0ubuntu1~24.04.1" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 25.10 · dotnet10 · FIXED · 10.0.104-10.0.4-0ubuntu1~25.10.1

sudo apt update && sudo apt install --only-upgrade dotnet10 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' dotnet10)" ge "10.0.104-10.0.4-0ubuntu1~25.10.1" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 22.04 · dotnet6 · NOT AFFECTED

Ubuntu 22.04 · dotnet8 · NOT AFFECTED

Ubuntu 24.04 · dotnet8 · NOT AFFECTED

RHEL 10 · dotnet9.0 · FIXED · dotnet9.0-9.0.115-1.el10_1

sudo dnf upgrade --advisory=RHSA-2026:4450 rpm -q dotnet9.0

RHEL 10 · dotnet10.0 · FIXED · dotnet10.0-10.0.104-1.el10_1

sudo dnf upgrade --advisory=RHSA-2026:4453 rpm -q dotnet10.0

RHEL 10.0 Extended Update Support · dotnet9.0 · FIXED · dotnet9.0-9.0.115-1.el10_0

sudo dnf upgrade --advisory=RHSA-2026:10083 rpm -q dotnet9.0

RHEL 8 · dotnet9.0 · FIXED · dotnet9.0-9.0.115-1.el8_10

sudo dnf upgrade --advisory=RHSA-2026:4443 rpm -q dotnet9.0

RHEL 8 · dotnet10.0 · FIXED · dotnet10.0-10.0.104-1.el8_10

sudo dnf upgrade --advisory=RHSA-2026:4458 rpm -q dotnet10.0

Alpine 3.21 · dotnet9-runtime · FIXED · dotnet9-runtime-9.0.14-r0

apk add --upgrade dotnet9-runtime apk info -v dotnet9-runtime

Alpine 3.22 · dotnet9-runtime · FIXED · dotnet9-runtime-9.0.14-r0

apk add --upgrade dotnet9-runtime apk info -v dotnet9-runtime

Alpine 3.23 · dotnet10-runtime · FIXED · dotnet10-runtime-10.0.4-r0

apk add --upgrade dotnet10-runtime apk info -v dotnet10-runtime

Alpine 3.23 · dotnet9-runtime · FIXED · dotnet9-runtime-9.0.14-r0

apk add --upgrade dotnet9-runtime apk info -v dotnet9-runtime

Amazon Linux 2023 · see advisory · FIXED · ALAS2023-2026-1506 · source

sudo dnf update --advisory=ALAS2023-2026-1506

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-2026-26127?

.net: upgrade to 9.0.14, 10.0.4; bcl.memory: upgrade to 9.0.14, 10.0.4. Exact commands for each OS are on this page.

Is CVE-2026-26127 being exploited?

CVE-2026-26127 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-2026-26127 affect?

CVE-2026-26127 affects .net, bcl.memory. Severity is high (CVSS 7.5). Out-of-bounds read in .NET allows an unauthorized attacker to deny service over a network.

How urgent is CVE-2026-26127?

Priority 57/100. High severity; Remotely exploitable, no login, no user action; On your watchlist

Related CVEs

CVE-2026-70354 HIGH 7.8 UPGRADE UPGRADE Out-of-bounds write in .NET allows an unauthorized attacker to execute code locally.
CVE-2026-62898 HIGH 7.5 UPGRADE UPGRADE Use after free in Microsoft QUIC allows an unauthorized attacker to disclose information over a network.
CVE-2026-62886 HIGH 7.8 UPGRADE UPGRADE Integer overflow or wraparound in .NET allows an unauthorized attacker to elevate privileges locally.
CVE-2026-62871 HIGH 7.8 UPGRADE UPGRADE Out-of-bounds write in .NET allows an unauthorized attacker to execute code locally.
CVE-2026-62909 HIGH 7.8 UPGRADE UPGRADE Uncaught exception in .NET allows an authorized attacker to elevate privileges locally.

References

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