CVE-2025-7635: Unauthenticated Telnet access vulnerability in Calix GigaCenter ONT allows root access.This issue affects Giga

Routine

HIGH 7.7DOWNGRADE

CVE-2025-7635 is a high-severity flaw (CVSS 7.7) affecting calix gigacenter ont. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Unauthenticated Telnet access vulnerability in Calix GigaCenter ONT allows root access.This issue affects GigaCenter ONT: 844E, 844G, 844GE, 854GE.

Why this priority

High severity
Public exploit reference

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.7 (High)
Attack vector	Local
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 71%)
CISA exploited list	No
Weakness	CWE-306
Published	2025-09-09
Last modified	2026-06-17

Publisher (CNA): Fluid Attacks · Vendor: calix

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

Am I affected?

Timeline

2025-09-09 20:15 UTCPublished CVE record published
2026-06-17 10:05 UTCUpdated Record last modified

calix calix gigacenter ont DOWNGRADE

Affected: all versions · 844e · 844g · 844ge · 854ge

Fixed in: no fixed release known

Safe to downgrade to: a release before 844e

1. Check installed version

apt-cache policy calix-gigacenter-ont || rpm -q calix-gigacenter-ont || calix-gigacenter-ont --version

2. No fixed release: DOWNGRADE to a release before 844e (Debian / Ubuntu)

apt-cache madison calix-gigacenter-ont sudo apt install calix-gigacenter-ont=<VERSION_BEFORE_844e> sudo apt-mark hold calix-gigacenter-ont

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

dnf --showduplicates list calix-gigacenter-ont sudo dnf downgrade calix-gigacenter-ont-<VERSION_BEFORE_844e> sudo dnf versionlock add calix-gigacenter-ont

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-2025-7635?

calix gigacenter ont: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2025-7635 being exploited?

CVE-2025-7635 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-2025-7635 affect?

CVE-2025-7635 affects calix gigacenter ont. Severity is high (CVSS 7.7). Unauthenticated Telnet access vulnerability in Calix GigaCenter ONT allows root access.This issue affects GigaCenter ONT: 844E, 844G, 844GE, 854GE.

How urgent is CVE-2025-7635?

Priority 39/100. High severity; Public exploit reference

References

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