CVE-2026-15811: Kronosnet Information Disclosure Flaw

CVE-2026-15811 Overview

CVE-2026-15811 affects Kronosnet versions <=1.34, a network abstraction layer used by high-availability clustering software. The framework fails to zero-out sensitive memory regions after cryptographic configuration changes. Raw encryption keys remain resident in memory after their containing structures are freed. A local attacker with the ability to disclose process memory can recover the active cluster encryption key. Successful exploitation enables decryption of cluster network traffic or injection of malicious packets into the cluster fabric. Packet injection against cluster communications can trigger high-availability instability and node fencing events. The vulnerability is tracked under [CWE-212: Improper Removal of Sensitive Information Before Storage or Transfer].

Critical Impact
A local attacker leveraging memory disclosure can recover active Kronosnet encryption keys, decrypt cluster traffic, and inject packets that destabilize high-availability clusters.

Affected Products

Kronosnet versions <=1.34
High-availability cluster stacks that link against libknet for encrypted node communication
Downstream distributions redistributing vulnerable Kronosnet builds (see Red Hat CVE-2026-15811 Advisory)

Discovery Timeline

2026-07-21 - CVE-2026-15811 published to NVD
2026-07-23 - Last updated in NVD database

Technical Details for CVE-2026-15811

Vulnerability Analysis

Kronosnet provides encrypted, redundant network transport for cluster software such as Corosync. The library maintains cryptographic key material in heap-allocated structures tied to its configuration state. When operators rotate keys or reconfigure the cryptographic profile, Kronosnet frees the old key structures without overwriting the underlying memory. The freed heap regions retain the raw key bytes until the allocator reissues them for unrelated data. Any attacker capable of reading process memory during that window can extract the active encryption key. With the key in hand, the attacker can passively decrypt intercepted cluster traffic or actively forge authenticated packets to peer nodes. Forged packets targeting cluster membership or fencing protocols can force node evictions and disrupt service availability.

Root Cause

The root cause is missing memory sanitization on the cryptographic configuration teardown path. The code frees buffers containing key material without calling a secure wipe routine such as memset_s or explicit_bzero beforehand. This maps directly to [CWE-212], where sensitive data is not properly removed before the containing resource is released. Compiler dead-store elimination can also strip naive memset calls, making explicit secure-erase primitives mandatory for key material.

Attack Vector

Exploitation requires local access with low privileges on a node running vulnerable Kronosnet. The attacker must chain the flaw with a separate memory disclosure primitive, such as a heap read from a co-resident process, a core dump, /proc/<pid>/mem access, or a swap file recovered from disk. Attack complexity is high because the freed heap region must be captured before reuse. Once the key is recovered, the attacker can decrypt captured cluster traffic offline or inject crafted packets into the cluster network to trigger membership changes.

No verified public proof-of-concept code is available. Refer to the Red Hat Bug Report #2500849 for vendor technical detail.

Detection Methods for CVE-2026-15811

Indicators of Compromise

Unexpected core dumps or memory snapshots of processes linking libknet on cluster nodes
Unauthorized reads against /proc/<pid>/mem or /proc/<pid>/maps for cluster daemons such as corosync
Anomalous cluster membership churn, unexpected fencing events, or corrupted totem traffic without a hardware cause

Detection Strategies

Audit for processes other than the cluster stack that open file descriptors against cluster daemon memory
Alert on new SUID binaries or debugger attachments (ptrace) targeting corosync or related processes
Correlate cluster log entries reporting decryption failures or replay-protection triggers with local user session activity

Monitoring Recommendations

Enable Linux audit rules on ptrace, process_vm_readv, and reads of /proc/*/mem for accounts outside the cluster service identity
Forward Corosync and Kronosnet logs to a central SIEM and baseline normal membership transition rates
Monitor for creation of unexpected core files under /var/lib/systemd/coredump/ associated with cluster processes

How to Mitigate CVE-2026-15811

Immediate Actions Required

Inventory all cluster nodes and identify Kronosnet builds at version <=1.34
Apply the vendor-supplied Kronosnet update as soon as it is available through your distribution
Restrict local shell access on cluster nodes to a minimal set of administrators and enforce multi-factor authentication
Rotate all Kronosnet cryptographic keys after patching to invalidate any previously exposed material

Patch Information

Refer to the Red Hat CVE-2026-15811 Advisory for fixed package versions and errata. Downstream consumers should track their distribution's Kronosnet updates and rebuild dependent cluster packages when required.

Workarounds

Disable core dumps for cluster daemons by setting LimitCORE=0 in the relevant systemd unit files
Restrict ptrace scope by setting kernel.yama.ptrace_scope=2 or 3 via sysctl to block cross-process memory reads
Encrypt swap partitions to prevent recovery of paged-out key material from disk
Segment the cluster interconnect onto a dedicated VLAN to limit exposure to injected packets

bash

# Harden cluster node against memory disclosure of Kronosnet keys
sysctl -w kernel.yama.ptrace_scope=2
echo 'kernel.yama.ptrace_scope=2' > /etc/sysctl.d/99-kronosnet.conf

# Disable core dumps for the cluster service
mkdir -p /etc/systemd/system/corosync.service.d
cat > /etc/systemd/system/corosync.service.d/override.conf <<EOF
[Service]
LimitCORE=0
EOF
systemctl daemon-reload
systemctl restart corosync