In the Linux kernel, the following vulnerability has been resolved:
RDMA/rxe: insert mcg into mcg_tree only after rxe_mcast_add() succeeds
rxe_get_mcg() publishes a newly allocated multicast group in
rxe->mcg_tree before programming the backing Ethernet multicast address
with rxe_mcast_add(), which runs outside mcg_lock. A local userspace
RDMA client reaches this path with ATTACH_MCAST on a UD QP; if
rxe_mcast_add() then returns an error (for example -ENODEV when the
backing netdev has been removed, or a propagated dev_mc_add() error),
the unwind frees the published group without removing it from the tree.
A later lookup of the same MGID dereferences the freed struct rxe_mcg
from __rxe_lookup_mcg().
Fix this by keeping the new mcg private until rxe_mcast_add() succeeds.
Split the tree publication into __rxe_publish_mcg(), call rxe_mcast_add()
before taking the tree reference, and free the still-private mcg on
failure. Because the group is never visible in mcg_tree until the
multicast address is programmed, no concurrent caller can look it up or
attach a QP to a group that is about to be torn down, so the error path
needs no conditional unwind. If another caller publishes the same MGID
while the address is being programmed, the post-add re-check under
mcg_lock finds the winner; this caller then drops its private object and
balances its own rxe_mcast_add() with rxe_mcast_del() before returning
the winner.
Reproduced by forcing the rxe_mcast_add() error return under KASAN:
without the change the next attach to the same MGID reports a
slab-use-after-free in __rxe_lookup_mcg(); with it the forced failure
returns cleanly. A no-injection attach/detach regression, including a
two-QP shared join/leave and re-attach, stays KASAN- and leak-clean.
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