In the Linux kernel, the following vulnerability has been resolved:
net: stmmac: TSO: Fix unbalanced DMA map/unmap for non-paged SKB data
In case the non-paged data of a SKB carries protocol header and protocol
payload to be transmitted on a certain platform that the DMA AXI address
width is configured to 40-bit/48-bit, or the size of the non-paged data
is bigger than TSO_MAX_BUFF_SIZE on a certain platform that the DMA AXI
address width is configured to 32-bit, then this SKB requires at least
two DMA transmit descriptors to serve it.
For example, three descriptors are allocated to split one DMA buffer
mapped from one piece of non-paged data:
dma_desc[N + 0],
dma_desc[N + 1],
dma_desc[N + 2].
Then three elements of tx_q->tx_skbuff_dma[] will be allocated to hold
extra information to be reused in stmmac_tx_clean():
tx_q->tx_skbuff_dma[N + 0],
tx_q->tx_skbuff_dma[N + 1],
tx_q->tx_skbuff_dma[N + 2].
Now we focus on tx_q->tx_skbuff_dma[entry].buf, which is the DMA buffer
address returned by DMA mapping call. stmmac_tx_clean() will try to
unmap the DMA buffer _ONLY_IF_ tx_q->tx_skbuff_dma[entry].buf
is a valid buffer address.
The expected behavior that saves DMA buffer address of this non-paged
data to tx_q->tx_skbuff_dma[entry].buf is:
tx_q->tx_skbuff_dma[N + 0].buf = NULL;
tx_q->tx_skbuff_dma[N + 1].buf = NULL;
tx_q->tx_skbuff_dma[N + 2].buf = dma_map_single();
Unfortunately, the current code misbehaves like this:
tx_q->tx_skbuff_dma[N + 0].buf = dma_map_single();
tx_q->tx_skbuff_dma[N + 1].buf = NULL;
tx_q->tx_skbuff_dma[N + 2].buf = NULL;
On the stmmac_tx_clean() side, when dma_desc[N + 0] is closed by the
DMA engine, tx_q->tx_skbuff_dma[N + 0].buf is a valid buffer address
obviously, then the DMA buffer will be unmapped immediately.
There may be a rare case that the DMA engine does not finish the
pending dma_desc[N + 1], dma_desc[N + 2] yet. Now things will go
horribly wrong, DMA is going to access a unmapped/unreferenced memory
region, corrupted data will be transmited or iommu fault will be
triggered :(
In contrast, the for-loop that maps SKB fragments behaves perfectly
as expected, and that is how the driver should do for both non-paged
data and paged frags actually.
This patch corrects DMA map/unmap sequences by fixing the array index
for tx_q->tx_skbuff_dma[entry].buf when assigning DMA buffer address.
Tested and verified on DWXGMAC CORE 3.20a
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (5.5): severity, escalated by confirmed exploitation. This CVE's 5.5 is its impact severity (EG Severity), not escalated.
- EG Severity
- 5.5 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 0.6% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-07). 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 every mission impact level.CISA BOD 26-04: 60 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 every mission impact level.
A fix is available. Apply it within your standard update timelines.
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (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)60 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 partial (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