CVE-2024-27043 Overview
CVE-2024-27043 is a use-after-free vulnerability [CWE-416] in the Linux kernel's Digital Video Broadcasting (DVB) subsystem. The flaw resides in the dvb_register_device function within drivers/media/dvb-core/dvbdev.c. When error-handling paths free the dvbdev structure, the caller-supplied pointer *pdvbdev is not reset to NULL. Subsequent operations dereference this dangling pointer, leading to use-after-free conditions during device teardown via dvb_unregister_device and kref_put.
The vulnerability affects local attackers with low privileges and can result in memory corruption, kernel crashes, or potential privilege escalation on systems running affected Linux kernel versions.
Critical Impact
Local attackers with low privileges can trigger memory corruption in the DVB subsystem, potentially leading to kernel crashes or privilege escalation through use-after-free exploitation.
Affected Products
- Linux Kernel (multiple stable branches prior to the patched commits)
- Debian LTS distributions shipping vulnerable kernel packages
- Downstream distributions using the affected dvb-core media driver
Discovery Timeline
- 2024-05-01 - CVE-2024-27043 published to NVD
- 2024-06 - Debian LTS security announcements released
- 2024-12-23 - Last updated in NVD database
Technical Details for CVE-2024-27043
Vulnerability Analysis
The vulnerability exists in the Linux kernel media subsystem, specifically in the DVB core driver (drivers/media/dvb-core/dvbdev.c). The dvb_register_device function assigns the freshly allocated dvbdev structure to the caller's *pdvbdev output pointer early in execution. If subsequent initialization steps fail, the function enters error-handling paths that free dvbdev but leave *pdvbdev pointing to the freed memory.
The consequence appears later in the device lifecycle. When code such as dvb_dmxdev_release invokes dvb_unregister_device on the dangling pointer, the kernel walks through dvb_remove_device and dvb_device_put, ultimately reaching kref_put on freed memory. This triggers reference counting on a stale allocation and can cause heap corruption.
The call chain illustrating the use-after-free is: budget_register → dvb_dmxdev_init → dvb_register_device (failure path frees dvbdev), followed later by dvb_dmxdev_release → dvb_unregister_device → dvb_remove_device → dvb_device_put → kref_put operating on the freed memory.
Root Cause
The root cause is missing pointer invalidation after deallocation. The error-handling paths in dvb_register_device free the dvbdev allocation but do not reset *pdvbdev to NULL. Calling code retains a pointer to memory that has been returned to the slab allocator, violating the kernel's pointer ownership model.
Attack Vector
Exploitation requires local access with low privileges on a system that exposes DVB devices or modules. An attacker capable of triggering DVB device registration failures, such as through racing device probe paths or constrained resource conditions, can force the kernel into the vulnerable error path. The dangling pointer is later dereferenced during normal device cleanup, producing the use-after-free condition without further attacker interaction.
The vulnerability mechanism is described in the upstream kernel commit messages. See the Kernel Git Commit Update 1 and related patches for technical details of the fix.
Detection Methods for CVE-2024-27043
Indicators of Compromise
- Kernel oops or panic messages referencing dvb_register_device, dvb_unregister_device, dvb_device_put, or kref_put in dmesg or /var/log/kern.log
- KASAN reports flagging use-after-free in drivers/media/dvb-core/dvbdev.c
- Unexpected crashes or reboots on systems with DVB hardware or modules loaded such as dvb-core, budget, or related media drivers
Detection Strategies
- Audit running kernel versions against the patched commits listed in the upstream advisories to identify unpatched hosts
- Enable Kernel Address Sanitizer (KASAN) in test environments to surface use-after-free conditions in DVB code paths
- Monitor module load events for dvb-core and dependent drivers on systems that do not require DVB functionality
Monitoring Recommendations
- Collect kernel ring buffer output centrally and alert on stack traces involving dvb_* symbols
- Track package versions of linux-image-* across the fleet and correlate against vendor advisories
- Review systemd journal entries for repeated DVB device registration failures that could indicate exploitation attempts
How to Mitigate CVE-2024-27043
Immediate Actions Required
- Apply the latest stable kernel update from your Linux distribution that includes the upstream fix
- On Debian systems, update kernel packages per the Debian LTS Announcement 1 and Debian LTS Announcement 2
- Reboot affected systems after patching to load the corrected kernel image
- Inventory systems with DVB hardware or media drivers loaded and prioritize them for patching
Patch Information
The upstream fix sets *pdvbdev to NULL after freeing dvbdev in error-handling paths, preventing the dangling pointer from propagating to callers. Patched commits are available across multiple stable branches, including 096237039d00, 0d3fe80b6d17, 35674111a043, 437a111f79a2, 779e8db7efb2, 8c64f4cdf4e6, b7586e902128, d0f5c2833382, and f20c3270f3ed. Refer to the Kernel Git Commit Update 2 for the canonical fix.
Workarounds
- Unload the dvb-core module and dependent drivers on systems that do not require DVB functionality using modprobe -r
- Blacklist DVB-related modules in /etc/modprobe.d/ to prevent automatic loading
- Restrict local user access on systems where DVB modules cannot be removed to reduce the exploitation surface
# Blacklist DVB modules on systems that do not require DVB support
echo "blacklist dvb_core" | sudo tee /etc/modprobe.d/blacklist-dvb.conf
echo "blacklist budget" | sudo tee -a /etc/modprobe.d/blacklist-dvb.conf
sudo update-initramfs -u
# Verify modules are not loaded after reboot
lsmod | grep -E 'dvb|budget'
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
