Listen to this Post
The vulnerability CVE-2025-39875 is a NULL pointer dereference flaw within the `igb` network driver of the Linux kernel. It is triggered during the execution of an `ethtool` loopback test on an affected network interface. The issue occurs because a dedicated test ring, set up for the loopback operation, does not have an associated `q_vector` structure, as interrupts are not typically used for these temporary rings. When the kernel attempts to set up RX resources for this ring, the `igb_setup_rx_resources` function incorrectly tries to access `rx_ring->q_vector->napi.napi_id` to register an XDP RX queue. Since the `q_vector` pointer for the test ring is NULL, this dereference causes a kernel crash. The root cause was a missed update following a prior kernel commit (5ef44b3cb43b) which removed the need for the `napi_id` parameter in the `__xdp_rxq_info_reg()` function. The fix, submitted in August 2025, simply passes a static value of `0` for this parameter instead of the NULL pointer, resolving the crash.
Platform:
Linux kernel
Version:
Various distributions
Vulnerability :
NULL pointer dereference
Severity:
Medium
Date:
2025-09-23
Prediction:
2026-Q1
What Undercode Say:
Analytics
– `uname -r` – Check kernel version.
– `ethtool -t eth0` – Trigger loopback test.
– `lsmod | grep igb` – Verify driver loaded.
– `dmesg | tail` – Check for crash logs.
How Exploit:
Exploitation Path
- Attacker requires local access.
- Low privileges are sufficient.
- Executes ethtool loopback command.
- No public exploit available.
Protection from this CVE
Mitigation Actions
- Apply kernel update.
- Restrict ethtool access.
- Monitor for patches.
Impact:
Primary Consequence
- System crash.
- Denial of Service.
- Availability loss.
🎯Let’s Practice Exploiting & Learn Patching For Free:
Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
Undercode
