SB2026060345 - Red Hat Enterprise Linux 9 update for kernel-rt
Published: June 3, 2026
Breakdown by Severity
- Low
- Medium
- High
- Critical
Description
This security bulletin contains information about 7 vulnerabilities.
1) Resource management error (CVE-ID: CVE-2025-39766)
CWE-ID: CWE-399 - Resource Management Errors
CVSSv4: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear
The vulnerability allows a local user to perform a denial of service (DoS) attack.
The vulnerability exists due to resource management error within the cake_enqueue() function in net/sched/sch_cake.c. A local user can perform a denial of service (DoS) attack.
2) Use After Free (CVE-ID: CVE-2026-23270)
CWE-ID: CWE-416 - Use After Free
CVSSv4: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear
The vulnerability allows a local user to cause a use-after-free condition.
The vulnerability exists due to improper memory management in the act_ct action handling within the net/sched subsystem when processing packets in the egress path. A local user can attach the act_ct action to non-clsact/ingress qdiscs and trigger packet classification that returns TC_ACT_CONSUMED while the socket buffer (skb) is still held by the defragmentation engine, leading to a use-after-free condition.
The vulnerability specifically arises when act_ct is used in contexts not designed to handle TC_ACT_CONSUMED, particularly outside clsact/ingress qdiscs and shared blocks. Exploitation requires the ability to configure traffic control (tc) actions, implying local access and privileges to modify qdisc configurations.
3) Use-after-free (CVE-ID: CVE-2026-31419)
CWE-ID: CWE-416 - Use After Free
CVSSv4: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear
The vulnerability allows a local user to cause a denial of service.
The vulnerability exists due to a use-after-free in bond_xmit_broadcast() when transmitting broadcast packets during concurrent slave enslave or release operations. A local user can trigger concurrent network interface state changes and packet transmission to cause a denial of service.
The issue arises because the determination of the last slave can change during RCU-protected iteration, leading to double consumption and double free of the original skb.
4) Stack-based buffer overflow (CVE-ID: CVE-2026-43037)
CWE-ID: CWE-121 - Stack-based buffer overflow
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber
The vulnerability allows a remote attacker to execute arbitrary code.
The vulnerability exists due to a stack-based buffer overflow in ip4ip6_err() and __ip_options_echo() when processing a crafted packet that triggers ICMP error handling on a cloned skb. A remote attacker can send a specially crafted packet to execute arbitrary code.
The issue is caused by reusing skb cb[] data written by the IPv6 receive path as IPv4 metadata, allowing attacker-controlled packet data to influence the copied option length.
5) Out-of-bounds read (CVE-ID: CVE-2026-43038)
CWE-ID: CWE-125 - Out-of-bounds read
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to an out-of-bounds read in ip6_err_gen_icmpv6_unreach() when processing a forged ICMPv4 error containing a CIPSO IP option and an attacker-controlled inner IPv6 packet. A remote attacker can send a specially crafted ICMP error packet to cause a denial of service.
The issue arises because IPv4 control buffer data is reused as IPv6 control buffer data in a cloned skb, which can lead to a forged home address option offset being used during IPv6 TLV parsing.
6) Out-of-bounds read (CVE-ID: CVE-2026-31709)
CWE-ID: CWE-125 - Out-of-bounds read
CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to an out-of-bounds read in cifsacl DACL rewrite helpers when processing a server-supplied truncated DACL. A remote attacker can send a malformed ACL response to cause a denial of service.
The issue occurs because the incoming DACL body and each ACE were not structurally validated before chmod/chown security descriptor rebuild paths walked the ACE list.
7) Use-after-free (CVE-ID: CVE-2026-43163)
CWE-ID: CWE-416 - Use After Free
CVSSv4: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear
The vulnerability allows a local user to cause a denial of service.
The vulnerability exists due to a use-after-free race in write_page() when resizing an array while bitmap daemon work is iterating over bitmap->storage.filemap. A local user can trigger concurrent bitmap update and resize operations to cause a denial of service.
The issue occurs because the md thread can continue running during quiesce(), allowing concurrent access to freed pages.
Remediation
Install update from vendor's website.