5.5

CVE-2020-36789: can: dev: can_get_echo_skb(): prevent call to kfree_skb() in hard IRQ context

Modified
AliasesUBUNTU-CVE-2020-36789DEBIAN-CVE-2020-36789
Published 17-04-2025Last modified 11-05-2026

Vulnerability summary

CVE-2020-36789 is a medium (CVSS 5.5) NULL Pointer Dereference vulnerability in linux. EPSS estimates a 0.19% chance of exploitation in the next 30 days, higher than 8.7% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 5.5, local access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
5.5/10
010
Medium · v3.1 (CVE.org)
EPSS score
0.19%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 3 · Related 3
SUSE-SU-2025:01600-1SUSE-SU-2025:01633-1SUSE-SU-2025:1574-1

Timeline

  1. 17-04-2025
    PublishedVulnerability first disclosed.
  2. 11-05-2026
    Last modifiedVulnerability 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

5 scores · 4 sources · 2 versions

EPSS trend

Probability

0.19%

Chance of exploitation in the next 30 days

Percentile

9%

Versus all other CVEs

30-day change

No change 0.00 pp

From 0.19% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: local access, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.

Ubuntu96 products
  • linuxAll versions (No fix recorded) | < 4.4.0-198.230 | < 4.15.0-135.139 | < 5.4.0-59.65
  • linux-allwinner-5.19All versions (No fix recorded)
  • linux-aws< 4.4.0-1083.87 | < 4.4.0-1119.133 | < 4.15.0-1093.99 | < 5.4.0-1034.35
  • linux-aws-5.0All versions (No fix recorded)
  • linux-aws-5.11All versions (No fix recorded)
Linux2 products
  • linux≥ 39549eef3587f1c1e8c65c88a2400d10fd30ea17, < 248b71ce92d4f3a574b2537f9838f48e892618f4 | ≥ 39549eef3587f1c1e8c65c88a2400d10fd30ea17, < 451187b20431924d13fcfecc500d7cd2d9951bac | ≥ 39549eef3587f1c1e8c65c88a2400d10fd30ea17, < 3a922a85701939624484e7f2fd07d32beed00d25 | ≥ 39549eef3587f1c1e8c65c88a2400d10fd30ea17, < 7e4cf2ec0ca236c3e5f904239cec6efe1f3baf22 | ≥ 39549eef3587f1c1e8c65c88a2400d10fd30ea17, < ab46748bf98864f9c3f5559060bf8caf9df2b41e | ≥ 39549eef3587f1c1e8c65c88a2400d10fd30ea17, < 87530b557affe01c764de32dbeb58cdf47234574 | ≥ 39549eef3587f1c1e8c65c88a2400d10fd30ea17, < 2283f79b22684d2812e5c76fc2280aae00390365 | 2.6.31
  • 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
Debian1 product
  • linux< 5.9.9-1

3 vendors · 99 products

References

11 links
Show all 11 references