FreeSWITCH: Pre-authentication stack buffer overflow in mod_rtmp control-message handling
Only FreeSWITCH deployments that build and load mod_rtmp are affected, covering 1.11.1 and earlier, including all released 1.10.x and 1.11.x versions and current master. Fixed in 1.11.2.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- Fixed in 1.11.2
- Who is exposed
- Specific setups only
Do first: Check whether your setup matches what the bug needs. mod_rtmp is built and loaded Affected versions are 1.11.1 and earlier, including all released 1.10.x and 1.11.x versions and current master
- Last modified
- 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? →
- 20/100 · 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
FreeSWITCH's mod_rtmp module has a stack buffer overflow in its RTMP control-message handling that a remote attacker can trigger without logging in, using a single crafted message. The overflow can crash FreeSWITCH and end all active calls, though it has not been shown to allow control-flow hijacking.
Read the original description
FreeSWITCH is a Software Defined Telecom Stack enabling the digital transformation from proprietary telecom switches to a software implementation that runs on any commodity hardware. Prior to 1.11.2, rtmp_handle_control() rendered an RTMP user-control message into a 200-byte stack buffer using an unbounded sprintf loop controlled by the wire message length. A body of roughly 70 bytes or more overflowed the stack before any RTMP login, because the handshake authenticates neither side. The flaw affects deployments that build and load mod_rtmp, which is disabled in the stock build and configuration but commonly exposes a listener on TCP port 1935 when enabled. One unauthenticated message can crash FreeSWITCH and end every active call; the constrained ASCII hex output has not yielded control-flow hijacking. This issue is fixed in version 1.11.2.
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
- Severity7.5/10CVSS 7.5
- No patch0/5No signal
What would change the score
- Would score about 70 if added to CISA KEV
- Would score about 65 if CISA's SSVC rates exploitation active
What to do
Check whether your setup matches what the bug needs.
mod_rtmp is built and loaded Affected versions are 1.11.1 and earlier, including all released 1.10.x and 1.11.x versions and current masterUpgrade to a fixed version: 1.11.2.
Workaround: Leave mod_rtmp unloaded unless RTMP client support is required, or restrict access to the RTMP port to trusted client networks at the firewall.
Timeline
- CVE published
- First seen by cve.now
Affected versions
- signalwire freeswitch
fixed in 1.11.2
Evidence 3
- Advisory
- Repository
- Repository
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-116567
Is CVE-2026-116567 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 specially formed control message sent to the RTMP handling code, before any authentication, overflows a buffer on the stack. One message can crash the FreeSWITCH process, which ends every call the instance is handling.Source: github.com
Which versions are affected by CVE-2026-116567?
freeswitch: before 1.11.2.Source: cve.now feed data
Am I affected, and how do I check?
Affected versions are 1.11.1 and earlier, including all released 1.10.x and 1.11.x versions and current master. The issue applies only where mod_rtmp is built and loaded, so check the installed FreeSWITCH version and whether mod_rtmp is in the loaded modules.Source: github.com
How do I fix CVE-2026-116567?
Upgrade to FreeSWITCH 1.11.2 or later, which contains the fix. If an upgrade cannot happen yet, see the workaround for leaving mod_rtmp unloaded or restricting the RTMP port.Source: github.com