In the Linux kernel, the following vulnerability has been resolved:
sctp: check send stream number after wait_for_sndbuf
This patch fixes a corner case where the asoc out stream count may change
after wait_for_sndbuf.
When the main thread in the client starts a connection, if its out stream
count is set to N while the in stream count in the server is set to N - 2,
another thread in the client keeps sending the msgs with stream number
N - 1, and waits for sndbuf before processing INIT_ACK.
However, after processing INIT_ACK, the out stream count in the client is
shrunk to N - 2, the same to the in stream count in the server. The crash
occurs when the thread waiting for sndbuf is awake and sends the msg in a
non-existing stream(N - 1), the call trace is as below:
KASAN: null-ptr-deref in range [0x0000000000000038-0x000000000000003f]
Call Trace:
sctp_cmd_send_msg net/sctp/sm_sideeffect.c:1114 [inline]
sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1777 [inline]
sctp_side_effects net/sctp/sm_sideeffect.c:1199 [inline]
sctp_do_sm+0x197d/0x5310 net/sctp/sm_sideeffect.c:1170
sctp_primitive_SEND+0x9f/0xc0 net/sctp/primitive.c:163
sctp_sendmsg_to_asoc+0x10eb/0x1a30 net/sctp/socket.c:1868
sctp_sendmsg+0x8d4/0x1d90 net/sctp/socket.c:2026
inet_sendmsg+0x9d/0xe0 net/ipv4/af_inet.c:825
sock_sendmsg_nosec net/socket.c:722 [inline]
sock_sendmsg+0xde/0x190 net/socket.c:745
The fix is to add an unlikely check for the send stream number after the
thread wakes up from the wait_for_sndbuf.
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
- 0.1% 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