CVE
C-Kermit memory corruption in FTP client reply handling
- Exploited
- No known exploitation
- Fix
- Fixed in 11.1.515
- Who is exposed
- Specific setups only
Do first: Check whether your setup matches what the bug needs. Affected C-Kermit version range is 8.0.200 up to but not including 11.1.515 C-Kermit is used as an FTP client against a malicious or intercepted FTP server Built with TLS/SSL support (PBSZ reply path) Built with GSSAPI, Kerberos 4, or SRP support (ADAT reply path)
- Published
- Last modified
- Whether it needs action now or is a reference record, by fixed rules, with why. Last checked is when cve.now last re-read it.What do these mean? →
- Reference
- Last checked
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 21/100 · provisional
- 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? →
- Specific setups only
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
C-Kermit, an FTP client, has a buffer overflow in its handling of FTP server replies that can let a malicious or intercepted FTP server overwrite client memory. The attack is reached over the network without logging in, but it requires the user to take an action such as connecting to the attacker's server.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
Read the original description
C-Kermit 8.0.200 before 11.1.515 contains a buffer overflow vulnerability in getreply() in ckcftp.c that allows malicious FTP servers to overwrite client memory by sending overlong security replies. Attackers controlling or intercepting an FTP server can send long PBSZ replies after AUTH TLS, or long ADAT replies in GSSAPI, Kerberos 4, and SRP builds, overflowing the static reply_buf with attacker-controlled bytes.
Who should check
Teams running C-Kermit 8.0.200 through 11.1.515 as an FTP client, built with TLS/SSL, GSSAPI, Kerberos 4 or SRP support, connecting to FTP servers
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure12/25Specific setups only, reachable over the network without a login
- Reach?/20Unknown. No tracked technology or package matched
- Severity8.7/10CVSS 8.7
- No patch0/5No signal
What would change the score
- Would score about 71 if added to CISA KEV
- Would score about 66 if CISA's SSVC rates exploitation active
What to do
Check whether your setup matches what the bug needs.
Affected C-Kermit version range is 8.0.200 up to but not including 11.1.515 C-Kermit is used as an FTP client against a malicious or intercepted FTP server Built with TLS/SSL support (PBSZ reply path) Built with GSSAPI, Kerberos 4, or SRP support (ADAT reply path)Upgrade to a fixed version: 11.1.515.
Check your systems with an agent
Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.
Check whether my systems are affected by CVE-2026-129123 (C-Kermit 8.0.200 before 11.1.515 FTP Client Buffer Overflow via PBSZ and ADAT Replies), using the cve.now data below.
Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.
What cve.now has for CVE-2026-129123 (entry last updated 2026-11-13):
Affected:
- OpenKermit C-Kermit: from 8.0.200, fixed in 11.1.515
Fixed versions: 11.1.515.
Conditions (all must be true for the bug to be hit):
- Affected C-Kermit version range is 8.0.200 up to but not including 11.1.515 (source: https://www.vulncheck.com/advisories/c-kermit-8.0.200-before-11.1.515-ftp-client-buffer-overflow-via-pbsz-and-adat-replies)
- C-Kermit is used as an FTP client against a malicious or intercepted FTP server (source: https://www.vulncheck.com/advisories/c-kermit-8.0.200-before-11.1.515-ftp-client-buffer-overflow-via-pbsz-and-adat-replies)
- Built with TLS/SSL support (PBSZ reply path) (source: https://github.com/OpenKermit/ckermit/security/advisories/GHSA-c5px-7h4c-gj8p)
- Built with GSSAPI, Kerberos 4, or SRP support (ADAT reply path) (source: https://github.com/OpenKermit/ckermit/security/advisories/GHSA-c5px-7h4c-gj8p)
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
Attacker needs: network access, no login, a user action.
CISA KEV: CVE-2026-129123 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-129123 only. If you also check another CVE, look up its own KEV status; never assume it from this one.
How to check:
- Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory.
Verify against the linked advisories before concluding, and cite the date you read each one:
- https://github.com/OpenKermit/ckermit/security/advisories/GHSA-c5px-7h4c-gj8p
- https://github.com/OpenKermit/ckermit/commit/39ab009a365b97632e9975e1266fa618c4bdc59f
- https://github.com/OpenKermit/ckermit/commit/bec28a4d544031fa07a07aacba3df5dd1202ef69
- https://github.com/OpenKermit/ckermit/releases/tag/v11.1.515
- https://github.com/OpenKermit/ckermit/blob/v11.0.514/ckcftp.c#L11161
- https://www.vulncheck.com/advisories/c-kermit-8.0.200-before-11.1.515-ftp-client-buffer-overflow-via-pbsz-and-adat-replies
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.
Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.
Entry: https://cve.now/CVE-2026-129123
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-129123"}.Timeline
- CVE published
- First seen by cve.now
Affected versions
- OpenKermit C-Kermit
From 8.0.200 · fixed in 11.1.515
Evidence 7
Vendor advisory · 1
Establishes: Affected and fixed versions.
- Advisory
Other links · 5
- Patch
- Patch
- Repository
- Repository
- Link
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-129123
Is CVE-2026-129123 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
What does this mean?
A buffer overflow in C-Kermit's FTP client code lets a malicious or intercepted FTP server send overlong security replies that overwrite the client's memory, which could lead to remote code execution.Source: vulncheck.com, github.com
Which versions are affected by CVE-2026-129123?
C-Kermit: from 8.0.200 before 11.1.515.Source: cve.now feed data
Am I affected, and how do I check?
Versions from 8.0.200 up to but not including 11.1.515 are affected. The PBSZ path applies when C-Kermit is built with TLS/SSL support, and the ADAT path applies when it is built with GSSAPI, Kerberos 4, or SRP support.Source: vulncheck.com, github.com
How do I fix CVE-2026-129123?
No fixed version is named in the checked facts, so the vendor's patch ids are not available here. Check the OpenKermit advisory for the fixed release and the patch details.Source: vulncheck.com, github.com