CVE-2026-23300: linux NULL Pointer Dereference
Vulnerability summary
CVE-2026-23300 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 2.2% of scored vulnerabilities.
Advisory lineage
Upstream 0 · Downstream 31 · Related 29Timeline
- 25-03-2026PublishedVulnerability first disclosed.
- 15-10-2026Last modifiedVulnerability information updated.
Description
In the Linux kernel, the following vulnerability has been resolved: net: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop When a standalone IPv6 nexthop object is created with a loopback device (e.g., "ip -6 nexthop add id 100 dev lo"), fib6_nh_init() misclassifies it as a reject route. This is because nexthop objects have no destination prefix (fc_dst=::), causing fib6_is_reject() to match any loopback nexthop. The reject path skips fib_nh_common_init(), leaving nhc_pcpu_rth_output unallocated. If an IPv4 route later references this nexthop, __mkroute_output() dereferences NULL nhc_pcpu_rth_output and panics. Simplify the check in fib6_nh_init() to only match explicit reject routes (RTF_REJECT) instead of using fib6_is_reject(). The loopback promotion heuristic in fib6_is_reject() is handled separately by ip6_route_info_create_nh(). After this change, the three cases behave as follows: 1. Explicit reject route ("ip -6 route add unreachable 2001:db8::/64"): RTF_REJECT is set, enters reject path, skips fib_nh_common_init(). No behavior change. 2. Implicit loopback reject route ("ip -6 route add 2001:db8::/32 dev lo"): RTF_REJECT is not set, takes normal path, fib_nh_common_init() is called. ip6_route_info_create_nh() still promotes it to reject afterward. nhc_pcpu_rth_output is allocated but unused, which is harmless. 3. Standalone nexthop object ("ip -6 nexthop add id 100 dev lo"): RTF_REJECT is not set, takes normal path, fib_nh_common_init() is called. nhc_pcpu_rth_output is properly allocated, fixing the crash when IPv4 routes reference this nexthop.
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
0.00 pp
From 0.13% on 19-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Ubuntu153 products
- linuxAll versions (No fix recorded) | < 5.15.0-186.196 | < 6.8.0-136.136
- linux-allwinner-5.19All versions (No fix recorded)
- linux-awsAll versions (No fix recorded) | < 5.15.0-1112.119 | < 6.8.0-1061.64
- linux-aws-5.0All versions (No fix recorded)
- linux-aws-5.11All versions (No fix recorded)
Linux2 products
- linux≥ 493ced1ac47c48bb86d9d4e8e87df8592be85a0e, < 607e68c1b7c5a30c795571be1906d716e989a644 | ≥ 493ced1ac47c48bb86d9d4e8e87df8592be85a0e, < c11d7c56c2076ee9cd72004f1976fe0734df2ae9 | ≥ 493ced1ac47c48bb86d9d4e8e87df8592be85a0e, < b5062fc2150614c9ea8a611c2e0cb6e047ebfa3a | ≥ 493ced1ac47c48bb86d9d4e8e87df8592be85a0e, < b299121e7453d23faddf464087dff513a495b4fc | ≥ 493ced1ac47c48bb86d9d4e8e87df8592be85a0e, < f7c9f8e3607440fe39300efbaf46cf7b5eecb23f | ≥ 493ced1ac47c48bb86d9d4e8e87df8592be85a0e, < b3b5a037d520afe3d5276e653bc0ff516bbda34c | ≥ 493ced1ac47c48bb86d9d4e8e87df8592be85a0e, < 8650db85b4259d2885d2a80fbc2317ce24194133 | ≥ 493ced1ac47c48bb86d9d4e8e87df8592be85a0e, < 21ec92774d1536f71bdc90b0e3d052eff99cf093 | 5.3
- linux_kernel≥ 5.3, < 5.10.253 | ≥ 5.11, < 5.15.203 | ≥ 5.16, < 6.1.167 | ≥ 6.2, < 6.6.130 | ≥ 6.7, < 6.12.77 | ≥ 6.13, < 6.18.17 | ≥ 6.19, < 6.19.7 | 7.0:rc1 | 7.0:rc2
Debian1 product
- linux< 6.1.170-1 | < 6.12.85-1 | < 6.19.8-1
3 vendors · 156 products
