CVE-2024-49997 Overview
CVE-2024-49997 is an information disclosure vulnerability in the Linux kernel's lantiq_etop Ethernet driver. The flaw exists in the padding logic for Ethernet frames on Amazon-SE and Danube MAC controllers, which cannot pad packets in hardware. When software padding is applied, the driver does not zero the expanded buffer, causing residual kernel memory contents to be transmitted on the wire. Remote observers on the network segment can capture these frames and extract sensitive data. The issue is classified under [CWE-212] (Improper Removal of Sensitive Information Before Storage or Transfer). Linux kernel maintainers resolved the flaw by replacing the unsafe padding routine with skb_put_padto(), which zeros the expanded buffer before transmission.
Critical Impact
Attackers on the local network can passively capture Ethernet frames containing uninitialized kernel memory, leading to disclosure of potentially sensitive data.
Affected Products
- Linux Kernel (multiple stable branches prior to the fix commits)
- Linux Kernel 6.12-rc1
- Debian LTS distributions and Siemens industrial products bundling affected kernels (per advisories SSA-265688, SSA-355557, SSA-398330)
Discovery Timeline
- 2024-10-21 - CVE-2024-49997 published to the National Vulnerability Database
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2024-49997
Vulnerability Analysis
The lantiq_etop driver services Ethernet MAC blocks on Lantiq Amazon-SE and Danube SoCs. These MACs lack hardware padding, so the driver must extend short frames to the minimum Ethernet payload length in software. The pre-patch implementation grew the socket buffer without clearing the newly exposed region. Any bytes that previously resided in that memory, including kernel heap contents from prior allocations, were serialized directly onto the wire. Because these frames traverse standard Ethernet segments, an attacker positioned on the same broadcast domain or with access to any span port can passively harvest the disclosed bytes. The vulnerability requires no authentication and no user interaction from the target system.
Root Cause
The driver used a padding path that allocated additional skb tailroom without initializing it. Uninitialized kernel memory therefore became part of the transmitted frame payload. This maps to [CWE-212], where sensitive information is not removed before transfer.
Attack Vector
Exploitation is passive. An attacker captures traffic emitted by an affected device using tcpdump, wireshark, or a network tap. Frames shorter than 60 bytes trigger the padding path and expose kernel memory in the padding region. Correlating captured padding bytes across many small frames can leak fragments of kernel structures, cryptographic material, or other transient data. See the Kernel Git Commit - Fix for the corrective patch replacing the padding logic with skb_put_padto().
Detection Methods for CVE-2024-49997
Indicators of Compromise
- Small Ethernet frames originating from Lantiq Amazon-SE or Danube devices containing non-zero, non-repeating bytes in the padding region beyond the IP payload.
- Recurring high-entropy byte patterns in the trailing bytes of runt frames captured on network segments hosting affected hardware.
Detection Strategies
- Inspect packet captures for Ethernet frames padded to 60 bytes where trailing bytes deviate from the expected zero fill.
- Inventory embedded devices and SoCs to identify systems running the lantiq_etop driver on unpatched kernels.
- Correlate kernel version telemetry from managed Linux endpoints against the fixed commit set published on kernel.org.
Monitoring Recommendations
- Enable full-packet capture on network segments containing MIPS-based Lantiq embedded gateways for baseline analysis.
- Track kernel package updates on affected distributions through the Debian LTS Announcement and vendor bulletins.
- Alert on unexpected outbound short frames from industrial control devices covered by the Siemens Security Advisory - SSA-265688.
How to Mitigate CVE-2024-49997
Immediate Actions Required
- Apply the stable kernel updates that replace the padding routine with skb_put_padto() as tracked in the upstream commit series.
- Update Debian systems using the fixes described in the Debian LTS Announcement.
- For Siemens industrial products, apply firmware updates referenced in SSA-355557 and SSA-398330.
Patch Information
Upstream fixes are available across stable branches. Reference commits include 1097bf16501e, 185df159843d, 2bf4c101d7c9, 431b122933b1, 45c0de18ff2d, 469856f76f48, 60c068444c20, 905f06a34f96, and e66e38d07b31. Distribution maintainers have backported the change; deploy the latest kernel package provided by the vendor for the affected release train.
Workarounds
- Segment affected Lantiq-based devices onto isolated VLANs to limit which hosts can capture their traffic.
- Restrict physical and logical access to network segments carrying traffic from Amazon-SE and Danube hardware until kernels are patched.
- Where feasible, replace unmanaged switches with managed equipment that disables promiscuous access from untrusted ports.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
