Vulnerability in Linux kernel (CVE-2026-90078)
Summary
Vulnerability in Linux kernel (CVE-2026-90078). Risk of unauthorized operations or information disclosure.
Original description
The description as published by the source.
In the Linux kernel, the following vulnerability has been resolved:
net/sched: act_skbmod: fix length calculations and avoid invalid header warnings
syzbot reported a warning in skb_network_header_len() triggered
by tcf_skbmod_act():
!skb_transport_header_was_set(skb)
WARNING: CPU: 0 PID: 14949 at include/linux/skbuff.h:3243 skb_network_header_len include/linux/skbuff.h:3243 [inline]
WARNING: CPU: 0 PID: 14949 at net/sched/act_skbmod.c:55 tcf_skbmod_act+0xfe8/0x1810 net/sched/act_skbmod.c:55
There are a few issues in tcf_skbmod_act():
- Calling skb_network_header_len() assumes skb->transport_header is set,
which is not guaranteed when tcf_skbmod_act() runs at TC ingress. - Unconditionally calling skb_mac_header_len() at the beginning of
tcf_skbmod_act() triggers a warning on L3 devices (e.g. TUN) where the
MAC header is unset, evaluating to an underflowed garbage length. - On TC ingress, skb->data points to the network header. Adding the MAC
header length to the IP header length causes skb_ensure_writable() to
request more bytes than the actual IP packet length, dropping valid
short packets (e.g. 28-byte UDP/IPv4 packets).
Fix these by:
- Using skb_network_offset(skb) + sizeof(struct iphdr/ipv6hdr) for
SKBMOD_F_ECN so that the required length is correctly calculated on
both ingress (offset == 0) and egress (offset == mac_len). - Setting max_edit_len to ETH_HLEN for Ethernet header modifications
after validating ARPHRD_ETHER.
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-90078 has been found in Linux kernel.
Risk of unauthorized operations or information disclosure.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Linux kernel CVE-2026-90078" on the vendor's site.
CVE-2026-90078 (Linux kernel)
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (unclassified) exists in Linux kernel.
Check the vendor advisory for the affected versions of Linux kernel.
Severity: ?. Risk of unauthorized operations or information disclosure.
Update to the patched release per vendor advisory.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
Audit SBOM/dependencies for affected components.資産台帳・SBOM・依存マニフェストで Linux kernel を使っているサービスとバージョンを洗い出す。
-
2Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
References
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web nvd.nist.gov
- web github.com