CVE-2021-47765Public exploitHinoki check available

Application crash via oversized credential fields

Published Jan 15, 2026 · Updated Jan 15, 2026

Out-of-bounds write in Celestial Software AbsoluteTelnet 11.24 allows local users to crash the client through oversized input fields. The SSH username and error-report email handlers accept a 1,000-character value and terminate the application when the value is submitted. Reproduction requires interactive access to the Windows client and causes an application crash without reported confidentiality or integrity impact.

CVSS severity6.7
Medium
EPSS probability0.20%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Out-of-bounds write in Celestial Software AbsoluteTelnet 11.24 allows local users to crash the client through oversized input fields. The SSH username and error-report email handlers accept a 1,000-character value and terminate the application when the value is submitted. Reproduction requires interactive access to the Windows client and causes an application crash without reported confidentiality or integrity impact.

The record

CVE
CVE-2021-47765
Published
Jan 15, 2026
Updated
Jan 15, 2026
Vendor
Celestial Software
Product
AbsoluteTelnet
Classifications
CWE-787, T1499
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 15, 2026CVE publishedPublication date reported by the CVE source.
  2. Jan 15, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=11.24

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Celestial Software · AbsoluteTelnetversion=11.24

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
6.2VulnCheckCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
6.7VulnCheckCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1499Endpoint Denial of Service

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo