In the Linux kernel, the following vulnerability has been resolved:
batman-adv: Drop unmanaged ELP metric worker
The ELP worker needs to calculate new metric values for all neighbors
"reachable" over an interface. Some of the used metric sources require
locks which might need to sleep. This sleep is incompatible with the RCU
list iterator used for the recorded neighbors. The initial approach to work
around of this problem was to queue another work item per neighbor and then
run this in a new context.
Even when this solved the RCU vs might_sleep() conflict, it has a major
problems: Nothing was stopping the work item in case it is not needed
anymore - for example because one of the related interfaces was removed or
the batman-adv module was unloaded - resulting in potential invalid memory
accesses.
Directly canceling the metric worker also has various problems:
* cancel_work_sync for a to-be-deactivated interface is called with
rtnl_lock held. But the code in the ELP metric worker also tries to use
rtnl_lock() - which will never return in this case. This also means that
cancel_work_sync would never return because it is waiting for the worker
to finish.
* iterating over the neighbor list for the to-be-deactivated interface is
currently done using the RCU specific methods. Which means that it is
possible to miss items when iterating over it without the associated
spinlock - a behaviour which is acceptable for a periodic metric check
but not for a cleanup routine (which must "stop" all still running
workers)
The better approch is to get rid of the per interface neighbor metric
worker and handle everything in the interface worker. The original problems
are solved by:
* creating a list of neighbors which require new metric information inside
the RCU protected context, gathering the metric according to the new list
outside the RCU protected context
* only use rcu_trylock inside metric gathering code to avoid a deadlock
when the cancel_delayed_work_sync is called in the interface removal code
(which is called with the rtnl_lock held)
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
- 0.2% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-25). 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 (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.
The score's inputs: 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