CVE-2020-36789

Advisory lineage Upstream: 0 Downstream: 5
Modified
Published: 17 Apr 2025, 18:01
Last modified:11 May 2026, 13:42

Vulnerability Summary

Overall Risk (default)
low
22/100
CVSS Score
5.5 MEDIUM
v3.1 (cve.org)
EPSS Score
0.02% LOW
0% probability 0.00%
KEV
Not listed
Ransomware
No reports
Public exploits
None found
Dark Web
Not detected

Timeline

17 Apr 2025, 18:01
Published
Vulnerability first disclosed
11 May 2026, 13:42
Last Modified
Vulnerability information updated

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 Metrics

  • v3.1•MEDIUM•Score: 5.5CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS Trends

Current EPSS score: 0.02%• Percentile: 7%

Techniques & Countermeasures

  • CWE-476•NULL Pointer Dereference

    The product dereferences a pointer that it expects to be valid but is NULL.

Affected Systems

  • linux•linux

    ≥ 39549eef3587f1c1e8c65c88a2400d10fd30ea17, < 248b71ce92d4f3a574b2537f9838f48e892618f4 | ≥ 39549eef3587f1c1e8c65c88a2400d10fd30ea17, < 451187b20431924d13fcfecc500d7cd2d9951bac | ≥ 39549eef3587f1c1e8c65c88a2400d10fd30ea17, < 3a922a85701939624484e7f2fd07d32beed00d25 | ≥ 39549eef3587f1c1e8c65c88a2400d10fd30ea17, < 7e4cf2ec0ca236c3e5f904239cec6efe1f3baf22 | ≥ 39549eef3587f1c1e8c65c88a2400d10fd30ea17, < ab46748bf98864f9c3f5559060bf8caf9df2b41e | ≥ 39549eef3587f1c1e8c65c88a2400d10fd30ea17, < 87530b557affe01c764de32dbeb58cdf47234574 | ≥ 39549eef3587f1c1e8c65c88a2400d10fd30ea17, < 2283f79b22684d2812e5c76fc2280aae00390365 | 2.6.31

  • linux•linux_kernel

    ≥ 2.6.31, < 4.4.244 | ≥ 4.5, < 4.9.244 | ≥ 4.10, < 4.14.207 | ≥ 4.15, < 4.19.158 | ≥ 4.20, < 5.4.78 | ≥ 5.5, < 5.9.9 | 5.10:rc1 | 5.10:rc2

References (7)