CVE-2020-36789

MEDIUM EPSS 5.0%
Published Apr 17, 20251y ago · Modified Jun 17, 20262w ago
5.5 CVSS 3.1
Medium
Find Similar
Published Apr 17, 2025 1y ago
Last Modified Jun 17, 2026 2w ago

Description

In the Linux kernel, the following vulnerability has been resolved: can: dev: can_get_echo_skb(): prevent call to kfree_skb() in hard IRQ context If a driver calls can_get_echo_skb() during a hardware IRQ (which is often, but not always, the case), the 'WARN_ON(in_irq)' in net/core/skbuff.c#skb_release_head_state() might be triggered, under network congestion circumstances, together with the potential risk of a NULL pointer dereference. The root cause of this issue is the call to kfree_skb() instead of dev_kfree_skb_irq() in net/core/dev.c#enqueue_to_backlog(). This patch prevents the skb to be freed within the call to netif_rx() by incrementing its reference count with skb_get(). The skb is finally freed by one of the in-irq-context safe functions: dev_consume_skb_any() or dev_kfree_skb_any(). The "any" version is used because some drivers might call can_get_echo_skb() in a normal context. The reason for this issue to occur is that initially, in the core network stack, loopback skb were not supposed to be received in hardware IRQ context. The CAN stack is an exeption. This bug was previously reported back in 2017 in [1] but the proposed patch never got accepted. While [1] directly modifies net/core/dev.c, we try to propose here a smoother modification local to CAN network stack (the assumption behind is that only CAN devices are affected by this issue). [1] http://lore.kernel.org/r/57a3ffb6-3309-3ad5-5a34-e93c3fe3614d@cetitec.com

CVSS Details

Base Score
5.5
Exploitability
1.8
Impact
3.6
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Attack Vector Local
Attack Complexity Low
Privileges Required Low
User Interaction None
Scope Unchanged
Confidentiality None
Integrity None
Availability High

Threat Intelligence

EPSS Exploit Probability
5.0% percentile
Exploit & Patch Status
No Known Exploit
Patch Available

Weaknesses 1

CWE-476 NULL Pointer Dereference Memory Safety

Affected Products 8

VendorProductVersionRange
linuxlinux_kernel*≥2.6.31  –  <4.4.244
linuxlinux_kernel*≥4.5  –  <4.9.244
linuxlinux_kernel*≥4.10  –  <4.14.207
linuxlinux_kernel*≥4.15  –  <4.19.158
linuxlinux_kernel*≥4.20  –  <5.4.78
linuxlinux_kernel*≥5.5  –  <5.9.9
linuxlinux_kernel5.10any
linuxlinux_kernel5.10any

References 7

  • git.kernel.org https://git.kernel.org/stable/c/2283f79b22684d2812e5c76fc2280aae00390365
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/248b71ce92d4f3a574b2537f9838f48e892618f4
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/3a922a85701939624484e7f2fd07d32beed00d25
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/451187b20431924d13fcfecc500d7cd2d9951bac
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/7e4cf2ec0ca236c3e5f904239cec6efe1f3baf22
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/87530b557affe01c764de32dbeb58cdf47234574
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/ab46748bf98864f9c3f5559060bf8caf9df2b41e
    Patch

Remediation

  • git.kernel.org https://git.kernel.org/stable/c/2283f79b22684d2812e5c76fc2280aae00390365
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/248b71ce92d4f3a574b2537f9838f48e892618f4
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/3a922a85701939624484e7f2fd07d32beed00d25
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/451187b20431924d13fcfecc500d7cd2d9951bac
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/7e4cf2ec0ca236c3e5f904239cec6efe1f3baf22
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/87530b557affe01c764de32dbeb58cdf47234574
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/ab46748bf98864f9c3f5559060bf8caf9df2b41e
    Patch