PatchTheCVECVE-2026-55948: Use after free in Microsoft Office Excel allows an unauthorized attacker to execute code locally.
42
This month
HIGH 7.8WATCHLISTMITIGATEDOWNGRADEMITIGATE
CVE-2026-55948 is a high-severity flaw (CVSS 7.8) affecting 365 apps, excel, microsoft 365. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
Use after free in Microsoft Office Excel allows an unauthorized attacker to execute code locally.
Why this priority
- High severity
- On your watchlist
No fix is published yet: follow the downgrade or mitigation steps.
Risk facts
| CVSS score | 7.8 (High) |
| Attack vector | Local |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | Required |
| EPSS exploit chance | 0.5% (top 60%) |
| CISA exploited list | No |
| Weakness | CWE-416 |
| Published | 2026-07-14 |
| Last modified | 2026-07-16 |
Publisher (CNA): Microsoft Corporation · Vendor: microsoft
Last updated 2026-07-16 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
microsoft 365 apps MITIGATE
Affected: all versions
Fixed in: no fixed release known
Safe to downgrade to: no unaffected older release
1. Check installed version
apt-cache policy 365-apps || rpm -q 365-apps || 365-apps --version
No fixed or unaffected release known
Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.
microsoft excel DOWNGRADE
Affected: 2016
Fixed in: no fixed release known
Safe to downgrade to: a release before 2016
1. Check installed version
apt-cache policy excel || rpm -q excel || excel --version
2. No fixed release: DOWNGRADE to a release before 2016 (Debian / Ubuntu)
apt-cache madison excel
sudo apt install excel=<VERSION_BEFORE_2016>
sudo apt-mark hold excel
2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)
dnf --showduplicates list excel
sudo dnf downgrade excel-<VERSION_BEFORE_2016>
sudo dnf versionlock add excel
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 microsoft 365 MITIGATE
Affected: all versions
Fixed in: no fixed release known
Safe to downgrade to: no unaffected older release
1. Check installed version
apt-cache policy microsoft-365 || rpm -q microsoft-365 || microsoft-365 --version
No fixed or unaffected release known
Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.
microsoft office 2019 MITIGATE
Affected: all versions
Fixed in: no fixed release known
Safe to downgrade to: no unaffected older release
1. Check installed version
apt-cache policy office-2019 || rpm -q office-2019 || office-2019 --version
No fixed or unaffected release known
Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.
microsoft office 2021 MITIGATE
Affected: all versions
Fixed in: no fixed release known
Safe to downgrade to: no unaffected older release
1. Check installed version
apt-cache policy office-2021 || rpm -q office-2021 || office-2021 --version
No fixed or unaffected release known
Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.
microsoft office 2021 MITIGATE
Affected: all versions
Fixed in: no fixed release known
Safe to downgrade to: no unaffected older release
1. Check installed version
apt-cache policy office-2021 || rpm -q office-2021 || office-2021 --version
No fixed or unaffected release known
Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.
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.
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-2026-55948?
365 apps: mitigate or apply the listed mitigation; excel: downgrade or apply the listed mitigation; microsoft 365: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.
Is CVE-2026-55948 being exploited?
CVE-2026-55948 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-2026-55948 affect?
CVE-2026-55948 affects 365 apps, excel, microsoft 365. Severity is high (CVSS 7.8). Use after free in Microsoft Office Excel allows an unauthorized attacker to execute code locally.
How urgent is CVE-2026-55948?
Priority 42/100. High severity; On your watchlist
Software pages
Microsoft Office vulnerabilities
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