CVE-2026-58097: PPP Command Interface Buffer Overflow

CVE-2026-58097 Overview

CVE-2026-58097 is a heap-based buffer overflow [CWE-122] in the FreeBSD ppp(8) daemon. The mp_SetEnddisc() function copies a user-supplied Peer Selection Negotiation (PSN) endpoint discriminator value without validating its length. A local user with access to the ppp(8) command interface can trigger the overflow to crash the daemon or potentially execute arbitrary code as root.

Critical Impact
Local attackers with ppp(8) command interface access can achieve arbitrary code execution as root, leading to full system compromise.

Affected Products

FreeBSD operating system versions shipping the vulnerable ppp(8) daemon
Systems where ppp(8) command interface is exposed to local users
Refer to FreeBSD Security Advisory SA-26:60 for specific version details

Discovery Timeline

2026-08-26 - CVE-2026-58097 published to NVD
2026-08-27 - Last updated in NVD database

Technical Details for CVE-2026-58097

Vulnerability Analysis

The FreeBSD ppp(8) daemon implements Multilink PPP support, which uses an endpoint discriminator to identify remote peers across multiple links. The mp_SetEnddisc() function handles setting this discriminator value based on input received through the ppp(8) command interface.

The function accepts a user-supplied PSN endpoint value and copies it into a fixed-size destination buffer without performing length validation. Because ppp(8) typically runs with elevated privileges to manage network interfaces, memory corruption within the process yields root-level impact.

Exploitation requires local access to the command interface but no special privileges beyond that access. Successful exploitation can crash the daemon or corrupt heap metadata to redirect execution flow.

Root Cause

The root cause is the absence of bounds checking in mp_SetEnddisc() before copying the endpoint discriminator into a heap-allocated buffer. This classifies as a classic heap-based buffer overflow [CWE-122]. Attacker-controlled data of arbitrary length overwrites adjacent heap chunks and metadata.

Attack Vector

An attacker interacts with the ppp(8) command interface and issues a command that supplies an overlong PSN endpoint value. The vulnerable function copies this value into the undersized buffer, corrupting adjacent heap memory. A crafted payload can overwrite function pointers or heap chunk metadata to achieve arbitrary code execution in the context of the ppp(8) process, which runs as root.

No network-facing attack path exists. The attack vector is local and requires prior authentication or shell access with permission to invoke ppp(8) commands. See the FreeBSD Security Advisory SA-26:60 for technical details on the vulnerable code path.

Detection Methods for CVE-2026-58097

Indicators of Compromise

Unexpected crashes or core dumps produced by the ppp(8) daemon
Presence of unusually long endpoint discriminator strings in ppp(8) command history or configuration files
Unexplained root-owned processes spawned as children of ppp(8)
Modifications to /etc/ppp/ configuration files by non-administrative users

Detection Strategies

Monitor process crash telemetry for ppp(8) segmentation faults and abnormal terminations
Audit local user access to the ppp(8) command interface and configuration directories
Inspect system logs for repeated ppp invocations from unexpected user contexts
Correlate ppp(8) crashes with subsequent privilege escalation activity on the same host

Monitoring Recommendations

Enable core dump collection for the ppp(8) process and review dumps for signs of heap corruption
Track file integrity on /etc/ppp/ppp.conf and related configuration files
Log all invocations of the ppp binary along with the invoking user identity
Alert on any child process of ppp(8) that spawns a shell or executes unexpected binaries

How to Mitigate CVE-2026-58097

Immediate Actions Required

Apply the FreeBSD security patch referenced in FreeBSD Security Advisory SA-26:60 as soon as available
Restrict access to the ppp(8) command interface to trusted administrative users only
Review /etc/ppp/ permissions to ensure non-privileged users cannot invoke or configure ppp
Audit which local accounts require Multilink PPP functionality and remove access for those that do not

Patch Information

FreeBSD has published fixes through the FreeBSD Security Advisory SA-26:60. Administrators should apply base system patches via freebsd-update or rebuild from patched source per the advisory. Consult the FreeBSD Security Advisory SA-26:60 for supported branch versions and patch identifiers.

Workarounds

Remove the setuid bit from the ppp binary if Multilink PPP is not required in the environment
Restrict execute permissions on /usr/sbin/ppp to a dedicated administrative group
Disable ppp(8) entirely on hosts that do not require PPP connectivity
Use mandatory access control frameworks to constrain the ppp(8) process capabilities

bash

# Restrict ppp(8) execution to a trusted admin group
chgrp ppp_admins /usr/sbin/ppp
chmod 4750 /usr/sbin/ppp

# Verify who can invoke the binary
ls -l /usr/sbin/ppp

# Apply FreeBSD base system updates
freebsd-update fetch
freebsd-update install