telnetd in GNU Inetutils through 2.7 allows remote authentication bypass via a "-f root" value for the USER environment variable.
Affects telnetd in GNU Inetutils 1.9.3 through 2.7 when clients send the USER variable via telnet -a or --login. No vendor rating is given, and the facts list no fixed version.
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Listed in CISA KEV
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Actively exploited
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- 1 on Exploit-DB
- Exploitation: active
- Automatable: yes
- Technical impact: total
Summary
The telnet server (telnetd) included in GNU Inetutils software is affected. An attacker on the network can log in as root without a password by setting the USER environment variable to "-f root," which bypasses authentication.
Summarized by anthropic/claude-haiku-5.5. Verify details against the original sources.
Read the original description
telnetd in GNU Inetutils through 2.7 allows remote authentication bypass via a "-f root" value for the USER environment variable.
Timeline
- CVE published
- Added to CISA KEV
CISA has evidence of exploitation in the wild
- CISA SSVC assessment
Exploitation: active · Automatable: yes · Technical impact: total
- CISA remediation deadline
Due date for US federal agencies to patch
- Public exploit on Exploit-DB
EDB-52524
- Record last updated
- EPSS reached 10%
FIRST estimates at least a 10% chance of exploitation in the next 30 days
Affected versions
- GNU Inetutils
From 1.9.3 · through 2.7
References 10
gnu.org
lists.gnu.org
codeberg.org
vicarius.io
Exploit-DB
Questions about CVE-2026-24061
What does this mean?
A remote client can send a "-f root" value for the USER environment variable and be logged in as root without normal authentication.Source: lists.gnu.org
Am I affected, and how do I check?
telnetd in GNU Inetutils from 1.9.3 up to and including 2.7. The bug requires the client to use the telnet -a or --login option, so the telnetd version and whether clients use those options are the things to check.Source: lists.gnu.org
What should I do about it?
Apply the patch or upgrade to a newer Inetutils release that incorporates the fix. The facts do not name a specific fixed version.Source: lists.gnu.org
Is it being exploited?
Yes. CISA added it to its Known Exploited Vulnerabilities catalog on 2026-01-26, which means it has evidence of attacks. Public exploit code exists (Exploit-DB).Source: cisa.gov, cve.now feed data
What if there's no patch?
Disable the telnetd server, or configure telnetd to use a custom login tool that does not permit the -f parameter.Source: lists.gnu.org