In the Linux kernel, the following vulnerability has been resolved:
tipc: skb_linearize the head skb when reassembling msgs
It's not a good idea to append the frag skb to a skb's frag_list if
the frag_list already has skbs from elsewhere, such as this skb was
created by pskb_copy() where the frag_list was cloned (all the skbs
in it were skb_get'ed) and shared by multiple skbs.
However, the new appended frag skb should have been only seen by the
current skb. Otherwise, it will cause use after free crashes as this
appended frag skb are seen by multiple skbs but it only got skb_get
called once.
The same thing happens with a skb updated by pskb_may_pull() with a
skb_cloned skb. Li Shuang has reported quite a few crashes caused
by this when doing testing over macvlan devices:
[] kernel BUG at net/core/skbuff.c:1970!
[] Call Trace:
[] skb_clone+0x4d/0xb0
[] macvlan_broadcast+0xd8/0x160 [macvlan]
[] macvlan_process_broadcast+0x148/0x150 [macvlan]
[] process_one_work+0x1a7/0x360
[] worker_thread+0x30/0x390
[] kernel BUG at mm/usercopy.c:102!
[] Call Trace:
[] __check_heap_object+0xd3/0x100
[] __check_object_size+0xff/0x16b
[] simple_copy_to_iter+0x1c/0x30
[] __skb_datagram_iter+0x7d/0x310
[] __skb_datagram_iter+0x2a5/0x310
[] skb_copy_datagram_iter+0x3b/0x90
[] tipc_recvmsg+0x14a/0x3a0 [tipc]
[] ____sys_recvmsg+0x91/0x150
[] ___sys_recvmsg+0x7b/0xc0
[] kernel BUG at mm/slub.c:305!
[] Call Trace:
[]
[] kmem_cache_free+0x3ff/0x400
[] __netif_receive_skb_core+0x12c/0xc40
[] ? kmem_cache_alloc+0x12e/0x270
[] netif_receive_skb_internal+0x3d/0xb0
[] ? get_rx_page_info+0x8e/0xa0 [be2net]
[] be_poll+0x6ef/0xd00 [be2net]
[] ? irq_exit+0x4f/0x100
[] net_rx_action+0x149/0x3b0
...
This patch is to fix it by linearizing the head skb if it has frag_list
set in tipc_buf_append(). Note that we choose to do this before calling
skb_unshare(), as __skb_linearize() will avoid skb_copy(). Also, we can
not just drop the frag_list either as the early time.
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
- 0.7% 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 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