In the Linux kernel, the following vulnerability has been resolved:
bnxt: fix head underflow on XDP head-grow
The xdp.py test test_xdp_native_adjst_head_grow_data crashes when run on
a bnxt machine (and also crashes in NIPA).
It seems that the bug is an underflow in bnxt_rx_multi_page_skb, which
builds the skb head:
napi_build_skb(data_ptr - bp->rx_offset, rxr->rx_page_size);
The problem with this expression is that in page mode, rx_offset is:
bp->rx_offset = NET_IP_ALIGN + XDP_PACKET_HEADROOM;
Which evaluates (at least on x86_64) to 258.
The test test_xdp_native_adjst_head_grow_data tests a case where the
head is adjusted by -256.
When this test runs, data_ptr is shifted to frag_start + 2 (where
frag_start = page_address(page) + offset).
Then, bnxt_rx_multi_page_skb is invoked and the napi_build_skb
expression subtracts 258, landing at an address before frag_start. This
could be either the previous fragment or the previous physical page when
the offset is < 256 (e.g. if the fragment started at offset 0).
When the skb is freed, the page pool fragment reference is dropped on
either the wrong page or the wrong frag of the right page. In either
case, the corrupted reference count can lead to the page being
prematurely recycled while still in use. Once (incorrectly) recycled, it
can be handed out again and on driver teardown this would result in a
double free.
The commit under fixes updated this code to handle the case where the
native page size is >= 64k, but it unintentionally broke the head grow
case.
To fix this, add an offset field to struct bnxt_sw_rx_bd, mirroring the
existing offset field in struct bnxt_sw_rx_agg_bd. Populate it on
allocation and preserve it on reuse.
In bnxt_rx_multi_page_skb, use the newly added offset field to compute
the fragment start and pass that to napi_build_skb. Adjust the layout
with skb_reserve.
There are two cases, the non-adjustment case and the adjustment case.
In both cases, the skb is built at page_address(page) + offset to
account for the case where the native page size >= 64K and skb_reserve
is called with data_ptr - (page_address(page) + offset). That
difference equals bp->rx_offset when data_ptr was not moved, or
bp->rx_offset + xdp_adjust when XDP adjusted the head.
Re-running the failing test with this commit applied causes the test to
run successfully to completion.
The other rx_skb_func implementations don't have this issue.
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (9.8): severity, escalated by confirmed exploitation. This CVE's 9.8 is its impact severity (EG Severity), not escalated.
- EG Severity
- 9.8 CRITICALCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 0.5% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-12). 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; Attend at high (mission-essential systems).CISA BOD 26-04: 3 days if the affected system is publicly exposed; 60 days 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; Attend at high (mission-essential systems).
A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
Exploitation none (CISA Vulnrichment) · Automatable yes (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)3 days if the affected system is publicly exposed; 60 days if it is not.
The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable yes (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