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How CVE-2026-0268 Works
CVE-2026-0268 is a security control bypass vulnerability affecting the Prisma Access Agent on Linux systems. The weakness resides in how the agent enforces VPN routing policies on the Linux network stack.
The Prisma Access Agent is responsible for intercepting and tunneling all outbound traffic from the endpoint through the Prisma Access cloud security service, ensuring that corporate policies are applied and data is encrypted. On Linux, this enforcement is typically achieved through a combination of network namespaces, routing tables, iptables/nftables rules, and policy-based routing (PBR). The agent creates a virtual network interface (e.g., `tun0` or similar) and manipulates the system’s routing table to direct all traffic through this interface, except for traffic destined for the VPN gateway itself.
The vulnerability stems from an improper protection of alternate paths (CWE-424). During the agent’s initialization or runtime operation, it fails to adequately lock down or monitor all possible routes that a local authenticated user could manipulate. Specifically, the agent does not sufficiently protect against local modifications to the routing table, policy routing rules, or the use of network namespaces that could bypass the enforced tunnel.
A local attacker with low privileges (authenticated user) can exploit this flaw by adding custom routing entries, modifying existing ones, or using advanced routing features like multiple routing tables or network namespaces to redirect specific traffic—or all traffic—outside the VPN tunnel. For instance, the attacker could add a route for a sensitive subnet that points to the physical interface (eth0) instead of the VPN interface, effectively leaking that traffic in cleartext. Alternatively, they could use `ip rule` to create policy-based routing that bypasses the agent’s rules for certain source IPs, UIDs, or packet marks.
This bypass is possible because the Prisma Access Agent does not continuously monitor and enforce routing table integrity against local changes. It may set up the routing initially but fails to use mechanisms like the Linux `netfilter` hook or eBPF programs to enforce a strict, immutable policy that prevents local rerouting. The agent also does not appear to leverage mandatory access control (MAC) frameworks like AppArmor or SELinux to restrict the user’s ability to modify network configurations, nor does it use capabilities like `CAP_NET_ADMIN` in a way that prevents abuse.
The attack is local and requires an authenticated user session. The attacker does not need root privileges (though they need sufficient permissions to modify routing, which on many distributions is restricted to root or users with CAP_NET_ADMIN). However, if the agent runs with elevated privileges and the user is in a group with `CAP_NET_ADMIN` capabilities, or if the agent itself runs with insufficient privilege separation, this vulnerability can be exploited. The impact is that sensitive data that should be protected by the VPN tunnel can be sent in the clear, bypassing security inspections, encryption, and corporate access controls.
Palo Alto Networks has rated this vulnerability as MEDIUM with a CVSS v4.0 base score of 4.4 (Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/AU:N/R:U/V:D/RE:M/U:Amber). The attack vector is local, complexity is low, and no user interaction is required. The vulnerability affects Prisma Access Agent for Linux versions 25.7 through 26.2.0. It does not affect Windows, macOS, iOS, Android, or ChromeOS versions.
DailyCVE Form:
Platform: Linux
Version: 25.7–26.2.0
Vulnerability: Local VPN Bypass
Severity: MEDIUM (4.4)
date: 2026-06-10
Prediction: 2026-06-10
What Undercode Say
Analytics & Threat Intelligence:
- Attack Surface: Local authenticated users on Linux endpoints running Prisma Access Agent versions 25.7 to 26.2.0.
- Exploit Maturity: Unreported; no public exploit available as of the advisory date.
- EPSS Score: Low (no significant exploitation activity detected).
- CVSS v3.1 Base Score: 5.3 (Medium).
- CVSS v2 Base Score: 4.6 (Vector: AV:L/AC:L/Au:N/C:P/I:P/A:N).
- CWE: CWE-424 – Improper Protection of Alternate Path.
- Required Privileges: Low (authenticated user).
- Automatable: No.
- Response Effort: Moderate.
- Recovery: User.
- Value Density: Diffuse.
Bash Commands & Codes (Demonstration of the Flaw):
The following commands illustrate how a local attacker could potentially bypass the VPN tunnel by manipulating the routing table. These are for educational and defensive analysis purposes only.
1. Check current routing table to identify VPN interface (e.g., tun0)
ip route show
2. Add a custom route to redirect traffic for a specific subnet (e.g., 10.0.0.0/8)
through the physical interface (eth0) instead of the VPN tunnel.
This would leak traffic destined for that subnet outside the VPN.
sudo ip route add 10.0.0.0/8 via 192.168.1.1 dev eth0
3. Alternatively, use policy-based routing to bypass the VPN for specific
source IPs or user IDs (if the agent's rules are based on packet marks).
sudo ip rule add from 192.168.100.50 lookup 100
sudo ip route add default via 192.168.1.1 dev eth0 table 100
4. Verify that traffic is now bypassing the VPN tunnel.
curl --interface eth0 https://api.ipify.org
5. To monitor for such changes, use auditd to track routing table modifications.
sudo auditctl -w /etc/iproute2/rt_tables -p wa -k route_change
sudo auditctl -a always,exit -S add_route -S del_route -k route_change
6. Use nftables to log and potentially block unauthorized routing changes.
sudo nft add table inet filter
sudo nft add chain inet filter route_guard { type filter hook prerouting priority 0\; }
sudo nft add rule inet filter route_guard meta skuid != 0 oifname "eth0" counter drop
Exploit
The exploitation of CVE-2026-0268 is straightforward and does not require sophisticated techniques. A local authenticated attacker can perform the following steps:
1. Identify the VPN Interface: Use `ip route` or `ifconfig` to determine which interface is being used for the VPN tunnel (commonly `tun0` or utun).
2. Analyze the Routing Policy: Examine the main routing table and any policy routing rules (ip rule list) to understand how the agent enforces VPN routing. Look for packet marks, fwmarks, or specific routing tables used by the agent.
3. Add a Bypass Route: Using ip route add, the attacker can add a route for a specific destination (e.g., a corporate subnet, or `0.0.0.0/0` for all traffic) that points to the physical network interface (eth0, wlan0) instead of the VPN interface.
4. Leverage Policy Routing: If the agent uses policy-based routing, the attacker can add a new rule with a higher priority that matches their traffic (e.g., by source IP, UID, or packet mark) and directs it to a routing table that sends traffic out the physical interface.
5. Use Network Namespaces: The attacker could create a new network namespace and move the physical interface into it, effectively isolating it from the VPN agent’s control, then route traffic from that namespace outside the tunnel.
6. Verify Bypass: The attacker can then use tools like curl, wget, or `traceroute` to confirm that traffic is exiting via the physical interface and not the VPN tunnel, effectively bypassing the security controls.
Because the vulnerability lies in the agent’s failure to protect alternate paths, no special exploit code is required; standard Linux networking commands suffice.
Protection
To protect against CVE-2026-0268, the following measures are recommended:
1. Upgrade to a Patched Version: The primary and most effective mitigation is to upgrade the Prisma Access Agent for Linux to version 26.2.1 or later. This version contains the necessary fixes to properly protect alternate routing paths.
2. Apply Principle of Least Privilege: Restrict local user permissions on Linux endpoints. Ensure that users do not have `CAP_NET_ADMIN` capabilities or sudo privileges that allow modification of network routing tables. Use groups and sudoers rules to limit who can execute ip, route, and iptables/nftables commands.
3. Implement Mandatory Access Control: Use SELinux or AppArmor to enforce strict policies that prevent the Prisma Access Agent and other processes from modifying network configurations in unauthorized ways. Define policies that only allow the agent to make routing changes.
4. Monitor Routing Table Integrity: Deploy monitoring scripts or use auditd to track changes to the routing tables, policy routing rules, and network interfaces. Alert on any unauthorized modifications.
5. Use eBPF for Enforcement: Consider deploying eBPF-based programs that attach to the network stack and enforce that all outbound traffic must go through the VPN interface, regardless of local routing table changes.
6. Network-Level Controls: As a secondary defense, implement network-level firewalls and intrusion detection systems that can detect and block traffic that originates from VPN endpoints but is not encapsulated properly.
7. Endpoint Detection and Response (EDR): Use EDR solutions that can detect anomalous network behavior, such as traffic leaving the endpoint via non-VPN interfaces when the VPN is expected to be active.
Impact
The successful exploitation of CVE-2026-0268 has the following impacts:
– Confidentiality Breach (High): Sensitive corporate data that should be encrypted and inspected by the Prisma Access service can be transmitted in cleartext over the public internet. This exposes the data to eavesdropping, man-in-the-middle attacks, and unauthorized access.
– Integrity Compromise (Low): While the primary impact is on confidentiality, there is a low integrity impact as traffic can potentially be modified en route without the VPN’s integrity protections.
– Bypass of Security Controls: The VPN is a critical security boundary for remote access. By bypassing it, attackers can circumvent security policies such as DNS filtering, threat prevention, URL filtering, and data loss prevention (DLP) that are enforced by the Prisma Access service.
– Compliance Violations: Organizations subject to regulatory frameworks (e.g., GDPR, HIPAA, PCI-DSS) may face compliance violations if sensitive data is transmitted outside the protected VPN tunnel.
– Increased Attack Surface: Leaked traffic can expose internal network topology, IP addresses, and application patterns, providing valuable reconnaissance information to external attackers.
– No Impact on Other Platforms: The vulnerability is specific to the Linux agent and does not affect Windows, macOS, iOS, Android, or ChromeOS deployments.
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Sources:
Reported By: nvd.nist.gov
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