CVE-2021-47765: AbsoluteTelnet 11.24 contains a denial of service vulnerability that allows local attackers to crash the appli

Routine

MEDIUM 5.5DOWNGRADE

CVE-2021-47765 is a medium-severity flaw (CVSS 5.5) affecting absolutetelnet. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

AbsoluteTelnet 11.24 contains a denial of service vulnerability that allows local attackers to crash the application by manipulating username and error report fields. Attackers can trigger the crash by inserting 1000 characters into the username or email address fields, causing the application to become unresponsive.

Why this priority

Public exploit reference

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

Risk facts

CVSS score	5.5 (Medium)
Attack vector	Local
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.2% (top 91%)
CISA exploited list	No
Weakness	CWE-787
Published	2026-01-15
Last modified	2026-06-17

Publisher (CNA): VulnCheck · Vendor: celestialsoftware

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

Am I affected?

Timeline

2026-01-15 16:16 UTCPublished CVE record published
2026-06-17 04:18 UTCUpdated Record last modified

celestialsoftware absolutetelnet DOWNGRADE

Affected: 11.24

Fixed in: no fixed release known

Safe to downgrade to: a release before 11.24

1. Check installed version

apt-cache policy absolutetelnet || rpm -q absolutetelnet || absolutetelnet --version

2. No fixed release: DOWNGRADE to a release before 11.24 (Debian / Ubuntu)

apt-cache madison absolutetelnet sudo apt install absolutetelnet=<VERSION_BEFORE_11.24> sudo apt-mark hold absolutetelnet

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

dnf --showduplicates list absolutetelnet sudo dnf downgrade absolutetelnet-<VERSION_BEFORE_11.24> sudo dnf versionlock add absolutetelnet

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-2021-47765?

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

Is CVE-2021-47765 being exploited?

CVE-2021-47765 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-2021-47765 affect?

CVE-2021-47765 affects absolutetelnet. Severity is medium (CVSS 5.5). AbsoluteTelnet 11.24 contains a denial of service vulnerability that allows local attackers to crash the application by manipulating username and error report fields. Attackers can trigger the crash by inserting 1000 characters into the use

How urgent is CVE-2021-47765?

Priority 27/100. Public exploit reference

Related CVEs

CVE-2021-47764 MEDIUM 5.5 DOWNGRADE AbsoluteTelnet 11.24 contains a denial of service vulnerability that allows local attackers to crash the appli
CVE-2020-37166 MEDIUM 6.2 DOWNGRADE AbsoluteTelnet 11.12 contains a denial of service vulnerability in the SSH2 username input field that allows l
CVE-2020-37165 MEDIUM 6.2 UPGRADE AbsoluteTelnet 11.12 contains a denial of service vulnerability that allows local attackers to crash the appli
CVE-2020-37164 MEDIUM 6.2 UPGRADE AbsoluteTelnet 11.12 contains a denial of service vulnerability that allows local attackers to crash the appli

References

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