CVE-2026-63990: linux NULL Pointer Dereference
Vulnerability summary
CVE-2026-63990 is a medium (CVSS 5.5) NULL Pointer Dereference vulnerability in linux. EPSS estimates a 0.13% chance of exploitation in the next 30 days, higher than 2.4% of scored vulnerabilities.
Advisory lineage
Upstream 0 · Downstream 31 · Related 31Timeline
- 19-07-2026PublishedVulnerability first disclosed.
Description
In the Linux kernel, the following vulnerability has been resolved: bonding: refuse to enslave CAN devices syzbot reported a kernel paging request crash in can_rx_unregister() inside net/can/af_can.c. The crash occurs because a virtual CAN device (vxcan) is being enslaved to a bonding master. During the enslavement process, the bonding driver mutates and modifies the network device states to fit an Ethernet-like aggregation model. However, CAN devices operate on a completely different Layer 2 architecture, relying on the CAN mid-layer private data structure (can_ml_priv) instead of standard Ethernet structures. Since bonding does not initialize or maintain these CAN structures, subsequent operations on the half-enslaved interface (such as closing associated sockets via isotp_release) lead to a null-pointer dereference when accessing the CAN receiver lists. Bonding CAN interfaces is architecturally invalid as CAN lacks MAC addresses, ARP capabilities, and standard Ethernet link-layer mechanisms. While generic loopback devices are blocked globally in net/core/dev.c, virtual CAN devices bypass this check because they do not carry the IFF_LOOPBACK flag, despite acting as local software-loopbacks. Fix this by explicitly blocking network devices of type ARPHRD_CAN from being enslaved at the very beginning of bond_enslave(). This prevents illegal state mutations, eliminates the resulting KASAN crashes, and avoids potential memory leaks from incomplete socket cleanups. As the CAN support has been added a long time after bonding the Fixes-tag points to the introduction of ARPHRD_CAN that would have needed a specific handling in bonding_main.c.
CVSS metrics
3 scores · 3 sources · 1 version- OSV · UbuntuEcosystem advisory · calculated5.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- OSV · DebianEcosystem advisory · calculated5.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
0.13%
Chance of exploitation in the next 30 days
Percentile
2%
Versus all other CVEs
30-day change
-0.05 pp
From 0.18% on 21-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Ubuntu167 products
- linuxAll versions (No fix recorded) | < 5.15.0-198.208 | < 6.8.0-146.146 | < 7.0.0-28.28
- linux-allwinner-5.19All versions (No fix recorded)
- linux-awsAll versions (No fix recorded) | < 5.15.0-1117.124 | < 6.8.0-1066.69 | < 7.0.0-1009.9
- linux-aws-5.0All versions (No fix recorded)
- linux-aws-5.11All versions (No fix recorded)
Linux2 products
- linux≥ cd05acfe65ed2cf2db683fa9a6adb8d35635263b, < 69b78b5f3033272e53a2dc2dad675962654a5b38 | ≥ cd05acfe65ed2cf2db683fa9a6adb8d35635263b, < 41e8478c4cd896d3abbe33d41afc90c84ac66602 | ≥ cd05acfe65ed2cf2db683fa9a6adb8d35635263b, < f4d78a81f57df82e9d82a2c07471fed1a1235893 | ≥ cd05acfe65ed2cf2db683fa9a6adb8d35635263b, < 02f1c87ded33b43d48b4a1d665da15f2157b30d8 | ≥ cd05acfe65ed2cf2db683fa9a6adb8d35635263b, < 9ea8a648d9120f7652bcde1ce2c4ad66871af707 | ≥ cd05acfe65ed2cf2db683fa9a6adb8d35635263b, < 563090e5d450c665f70d955a39f9587afc7842eb | ≥ cd05acfe65ed2cf2db683fa9a6adb8d35635263b, < 8ba68464e4787b6a7ec938826e16124df20fd23d | 2.6.25
- linux_kernel≥ 2.6.25, < 5.15.210 | ≥ 5.16, < 6.1.176 | ≥ 6.2, < 6.6.143 | ≥ 6.7, < 6.12.93 | ≥ 6.13, < 6.18.35 | ≥ 6.19, < 7.0.12 | 7.1:rc1 | 7.1:rc2 | 7.1:rc3 | 7.1:rc4 | 7.1:rc5
Debian1 product
- linux< 6.1.176-1 | < 6.12.94-1 | < 7.0.12-1
3 vendors · 170 products
