CVE
Freeradius: stack-based buffer overflow via unbounded eap-sim identity length
- Exploited
- No known exploitation
- Fix
- See vendor advisory
- Who is exposed
- Specific setups only
Do first: Check whether your setup matches what the bug needs. The EAP-SIM submodule is explicitly enabled within the FreeRADIUS EAP module configuration.
- 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? →
- 35/100 · 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
The freeradius package in Red Hat Enterprise Linux has a stack-based buffer overflow in its EAP-SIM module, which handles authentication requests. A remote attacker can trigger it without logging in by sending specially crafted EAP-SIM messages, which crashes the service and causes a denial of service.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
Read the original description
A flaw was found in freeradius's Extensible Authentication Protocol Method for Subscriber Identity Module (EAP-SIM) module. When handling authentication requests, the server copies a client-supplied identity into an internal structure without properly checking its length against a fixed-size buffer. An unauthenticated remote attacker can exploit this issue by sending specially crafted EAP-SIM messages, triggering a stack buffer overflow that crashes the service and results in a Denial of Service (DoS).
Who should check
Teams running FreeRADIUS with the EAP-SIM submodule enabled on Red Hat Enterprise Linux 6, 7, 8, 9 or 10.
Read the source excerpt
“FreeRADIUS deployments are only susceptible if the EAP-SIM authentication submodule is explicitly enabled”
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure12/25Specific setups only, reachable over the network without a login
- Reach10/20Shipped in major Linux distributions
- Severity7.5/10CVSS 7.5
- No patch5/5No fixed version listed; see vendor advisory
What would change the score
- Would score about 85 if added to CISA KEV
- Would score about 80 if CISA's SSVC rates exploitation active
What to do
Check whether your setup matches what the bug needs.
The EAP-SIM submodule is explicitly enabled within the FreeRADIUS EAP module configuration.Workaround: Disable the EAP-SIM submodule in the FreeRADIUS configuration if SIM-based authentication is not required.
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-2026-127029 (Freeradius: stack-based buffer overflow via unbounded eap-sim identity length), 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-2026-127029 (entry last updated 2026-11-12):
Affected:
- Red Hat Red Hat Enterprise Linux 10: version range not reported
- Red Hat Red Hat Enterprise Linux 6: version range not reported
- Red Hat Red Hat Enterprise Linux 7: version range not reported
- Red Hat Red Hat Enterprise Linux 8: version range not reported
- Red Hat Red Hat Enterprise Linux 9: version range not reported
Fixed versions: none listed yet.
Conditions (all must be true for the bug to be hit):
- The EAP-SIM submodule is explicitly enabled within the FreeRADIUS EAP module configuration. (source: https://access.redhat.com/security/cve/cve-2026-127029)
Setup: the bug needs a feature or setting that is off by default or uncommon. Check whether each asset has it on.
Attacker needs: network access, no login, no user action.
Workaround: Disable the EAP-SIM submodule in the FreeRADIUS configuration if SIM-based authentication is not required. (source: https://www.cve.org/CVERecord?id=CVE-2026-127029)
CISA KEV: CVE-2026-127029 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-127029 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://bugzilla.redhat.com/show_bug.cgi?id=2572339
- https://access.redhat.com/security/cve/CVE-2026-127029
- https://github.com/FreeRADIUS/freeradius-server/commit/064567a08f3b9d9b4863fab6060fafe296ac7de9
- https://github.com/FreeRADIUS/freeradius-server/commit/e415f818dcdf91626e5e7314b3a4f819ab11f572
- https://www.cve.org/CVERecord?id=CVE-2026-127029
- https://access.redhat.com/security/cve/cve-2026-127029
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-2026-127029
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-2026-127029"}.Timeline
- CVE published
- First seen by cve.now
Affected versions
- freeradius
Version range not reported
- freeradius
Version range not reported
- freeradius
Version range not reported
- freeradius:3.0/freeradius
Version range not reported
- freeradius
Version range not reported
Evidence 6
CVE record · 2
Establishes: The identifier and description.
- Record
- Record
Write-ups · 1
Establishes: Technical detail and context.
- Report
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-127029
Is CVE-2026-127029 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 remote, unauthenticated client can send an overlong EAP-SIM identity that overflows a stack buffer in FreeRADIUS. The overflow crashes the service, causing a denial of service.Source: access.redhat.com, cve.org
Am I affected, and how do I check?
The checked facts list Red Hat Enterprise Linux 6, 7, 8, 9 and 10 as products, without specific package versions. The issue only applies when the EAP-SIM authentication submodule is explicitly enabled in the EAP module configuration, so check that section of the FreeRADIUS configuration on your systems.Source: access.redhat.com, cve.org
How do I fix CVE-2026-127029?
The checked facts name no fixed version or vendor patch identifiers for this vulnerability. Until one is published, the only remedy listed is the workaround of disabling the EAP-SIM submodule.Source: access.redhat.com, cve.org
What if there's no patch?
Disable the EAP-SIM submodule in the FreeRADIUS configuration if SIM-based authentication is not required. This removes the vulnerable code path while no fix is available.Source: access.redhat.com, cve.org