In the Linux kernel, the following vulnerability has been resolved:
net: nsh: Use correct mac_offset to unwind gso skb in nsh_gso_segment()
As the call trace shows, skb_panic was caused by wrong skb->mac_header
in nsh_gso_segment():
invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI
CPU: 3 PID: 2737 Comm: syz Not tainted 6.3.0-next-20230505 #1
RIP: 0010:skb_panic+0xda/0xe0
call Trace:
skb_push+0x91/0xa0
nsh_gso_segment+0x4f3/0x570
skb_mac_gso_segment+0x19e/0x270
__skb_gso_segment+0x1e8/0x3c0
validate_xmit_skb+0x452/0x890
validate_xmit_skb_list+0x99/0xd0
sch_direct_xmit+0x294/0x7c0
__dev_queue_xmit+0x16f0/0x1d70
packet_xmit+0x185/0x210
packet_snd+0xc15/0x1170
packet_sendmsg+0x7b/0xa0
sock_sendmsg+0x14f/0x160
The root cause is:
nsh_gso_segment() use skb->network_header - nhoff to reset mac_header
in skb_gso_error_unwind() if inner-layer protocol gso fails.
However, skb->network_header may be reset by inner-layer protocol
gso function e.g. mpls_gso_segment. skb->mac_header reset by the
inaccurate network_header will be larger than skb headroom.
nsh_gso_segment
nhoff = skb->network_header - skb->mac_header;
__skb_pull(skb,nsh_len)
skb_mac_gso_segment
mpls_gso_segment
skb_reset_network_header(skb);//skb->network_header+=nsh_len
return -EINVAL;
skb_gso_error_unwind
skb_push(skb, nsh_len);
skb->mac_header = skb->network_header - nhoff;
// skb->mac_header > skb->headroom, cause skb_push panic
Use correct mac_offset to restore mac_header and get rid of nhoff.
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
- EG Severity
- Not assessed: no CVSS publishedA missing CVSS is not a severity of zero.
- EG Likelihood
- 0.2% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-26). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- No SSVC decision: EchelonGraph has not assessed this CVECISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the BOD 26-04 block below.
BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). Where an input reads “CISA's BOD 26-04 default”, no one has published it for this CVE, and CISA's implementation guidance says: “If “Automatable” and “Technical Impact” information items about a CVE ID are not available and the CVE ID is not in the KEV Catalog, CISA will treat its values as “no” and “total,” respectively, until CISA or a third party provides metadata about the CVE ID. CISA will always provide the Vulnrichment data for a CVE ID listed in the KEV Catalog.” Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it