In the Linux kernel, the following vulnerability has been resolved:
rxrpc: Fix ACKALL packet handling
rxrpc_input_ackall() accepts ACKALL packets without checking whether the
call is in a state that can legitimately have outstanding transmit buffers.
A forged ACKALL can therefore reach a new service call in
RXRPC_CALL_SERVER_RECV_REQUEST before any reply packets have been queued.
In that state call->tx_top is zero and call->tx_queue is NULL, so
rxrpc_rotate_tx_window() dereferences a NULL txqueue and triggers a
null-pointer dereference.
Fix the handling of ACKALL packets by the following means:
(1) Add two new call states: RXRPC_CALL_CLIENT_PRE_SEND which indicates
that the client call is connected, but nothing has been transmitted as
yet; and RXRPC_CALL_CLIENT_AWAIT_ACK, which indicates that everything
has been transmitted at least once, but we're now waiting for the
stuff remaining in the Tx buffer to be ACK'd (retransmissions may
still happen).
The RXRPC_CALL_CLIENT_PRE_SEND state is set when the call is assigned
a channel and transitions to RXRPC_CALL_CLIENT_SEND_REQUEST when the
first packet is transmitted.
RXRPC_CALL_CLIENT_AWAIT_REPLY is then narrowed in scope to indicate
that all Tx packets have been ACK'd and we're now waiting for the
reply to be received.
(2) As per Wyatt Feng's original patch[1], the ACKALL handler then checks
that the call state is one in which there might be stuff in the Tx
buffer to ACK, but now this includes AWAIT_ACK rather than
AWAIT_REPLY. ACKALL packets are ignored if received in the wrong
state.
Note that unlike Wyatt Feng's patch, it's no longer necessary to check
to see if the Tx buffer exists as this the state set now covers this.
(3) Make the ACKALL handler use call->tx_transmitted rather than
call->tx_top as the former is explicitly the highest packet seq number
transmitted, whereas the latter has a looser definition.
Thanks to Jeffrey Altman for a description of the history of the ACKALL
packet[1].
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (7.5): severity, escalated by confirmed exploitation. This CVE's 7.5 is its impact severity (EG Severity), not escalated.
- EG Severity
- 7.5 HIGHCVSS-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 2026-10-17). 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: 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 (no CISA value, KEV listing or exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from 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.
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