CVE-2025-20335: A vulnerability in the directory permissions of Cisco Desk Phone 9800 Series, Cisco IP Phone 7800 and 8800 Ser
31
Routine
MEDIUM 5.3REMOTEMITIGATEMITIGATEMITIGATE
CVE-2025-20335 is a medium-severity flaw (CVSS 5.3) affecting desk phone 9841 firmware, desk phone 9851 firmware, desk phone 9861 firmware. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
A vulnerability in the directory permissions of Cisco Desk Phone 9800 Series, Cisco IP Phone 7800 and 8800 Series, and Cisco Video Phone 8875 could allow an unauthenticated, remote attacker to write arbitrary files on an affected device.
This vulnerability is due to a lack of proper authentication controls. An attacker could exploit this vulnerability by sending a crafted request to an affected device. A successful exploit could allow the atta
Why this priority
Remotely exploitable, no login, no user action
No fix is published yet: follow the downgrade or mitigation steps.
Last updated 2026-06-17 · 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
cisco desk phone 9841 firmware MITIGATE
Affected: >= 3.0\(1\) and < 3.3\(1\)
Fixed in: 3.3\(1\)
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
cisco desk phone 9851 firmware MITIGATE
Affected: >= 3.0\(1\) and < 3.3\(1\)
Fixed in: 3.3\(1\)
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
cisco desk phone 9861 firmware MITIGATE
Affected: >= 3.0\(1\) and < 3.3\(1\)
Fixed in: 3.3\(1\)
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
cisco desk phone 9871 firmware MITIGATE
Affected: >= 3.0\(1\) and < 3.3\(1\)
Fixed in: 3.3\(1\)
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
cisco ip phone 7811 firmware MITIGATE
Affected: < 14.3\(1\) · 14.3\(1\) · 14.3\(1\) sr1
Fixed in: 14.3\(1\)
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
cisco ip phone 7821 firmware MITIGATE
Affected: < 14.3\(1\) · 14.3\(1\) · 14.3\(1\) sr1
Fixed in: 14.3\(1\)
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
Verify at the official sourceNVD · 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-2025-20335?
desk phone 9841 firmware: mitigate or apply the listed mitigation; desk phone 9851 firmware: mitigate or apply the listed mitigation; desk phone 9861 firmware: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.
Is CVE-2025-20335 being exploited?
CVE-2025-20335 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-2025-20335 affect?
CVE-2025-20335 affects desk phone 9841 firmware, desk phone 9851 firmware, desk phone 9861 firmware. Severity is medium (CVSS 5.3). A vulnerability in the directory permissions of Cisco Desk Phone 9800 Series, Cisco IP Phone 7800 and 8800 Series, and Cisco Video Phone 8875 could allow an unauthenticated, remote attacker to write arbitrary files on an affected device.
How urgent is CVE-2025-20335?
Priority 31/100. Remotely exploitable, no login, no user action
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