In the Linux kernel, the following vulnerability has been resolved:
netfilter: nft_objref: validate objref and objrefmap expressions
Referencing a synproxy stateful object from OUTPUT hook causes kernel
crash due to infinite recursive calls:
BUG: TASK stack guard page was hit at 000000008bda5b8c (stack is 000000003ab1c4a5..00000000494d8b12)
[...]
Call Trace:
__find_rr_leaf+0x99/0x230
fib6_table_lookup+0x13b/0x2d0
ip6_pol_route+0xa4/0x400
fib6_rule_lookup+0x156/0x240
ip6_route_output_flags+0xc6/0x150
__nf_ip6_route+0x23/0x50
synproxy_send_tcp_ipv6+0x106/0x200
synproxy_send_client_synack_ipv6+0x1aa/0x1f0
nft_synproxy_do_eval+0x263/0x310
nft_do_chain+0x5a8/0x5f0 [nf_tables
nft_do_chain_inet+0x98/0x110
nf_hook_slow+0x43/0xc0
__ip6_local_out+0xf0/0x170
ip6_local_out+0x17/0x70
synproxy_send_tcp_ipv6+0x1a2/0x200
synproxy_send_client_synack_ipv6+0x1aa/0x1f0
[...]
Implement objref and objrefmap expression validate functions.
Currently, only NFT_OBJECT_SYNPROXY object type requires validation.
This will also handle a jump to a chain using a synproxy object from the
OUTPUT hook.
Now when trying to reference a synproxy object in the OUTPUT hook, nft
will produce the following error:
synproxy_crash.nft: Error: Could not process rule: Operation not supported
synproxy name mysynproxy
^^^^^^^^^^^^^^^^^^^^^^^^
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (7.8): severity, escalated by confirmed exploitation. This CVE's 7.8 is its impact severity (EG Severity), not escalated.
- EG Severity
- 7.8 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 0.2% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-03). 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
- SSVC Track at medium mission impactTrack at low or medium mission impact; Track* at high (mission-essential systems).CISA 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 SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).
A fix is available. Apply it within your standard update timelines.
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
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 Vulnrichment) · Technical impact total (CISA Vulnrichment). 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