In the Linux kernel, the following vulnerability has been resolved:
net/9p: fix double req put in p9_fd_cancelled
Syzkaller reports a KASAN issue as below:
general protection fault, probably for non-canonical address 0xfbd59c0000000021: 0000 [#1] PREEMPT SMP KASAN NOPTI
KASAN: maybe wild-memory-access in range [0xdead000000000108-0xdead00000000010f]
CPU: 0 PID: 5083 Comm: syz-executor.2 Not tainted 6.1.134-syzkaller-00037-g855bd1d7d838 #0
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
RIP: 0010:__list_del include/linux/list.h:114 [inline]
RIP: 0010:__list_del_entry include/linux/list.h:137 [inline]
RIP: 0010:list_del include/linux/list.h:148 [inline]
RIP: 0010:p9_fd_cancelled+0xe9/0x200 net/9p/trans_fd.c:734
Call Trace:
p9_client_flush+0x351/0x440 net/9p/client.c:614
p9_client_rpc+0xb6b/0xc70 net/9p/client.c:734
p9_client_version net/9p/client.c:920 [inline]
p9_client_create+0xb51/0x1240 net/9p/client.c:1027
v9fs_session_init+0x1f0/0x18f0 fs/9p/v9fs.c:408
v9fs_mount+0xba/0xcb0 fs/9p/vfs_super.c:126
legacy_get_tree+0x108/0x220 fs/fs_context.c:632
vfs_get_tree+0x8e/0x300 fs/super.c:1573
do_new_mount fs/namespace.c:3056 [inline]
path_mount+0x6a6/0x1e90 fs/namespace.c:3386
do_mount fs/namespace.c:3399 [inline]
__do_sys_mount fs/namespace.c:3607 [inline]
__se_sys_mount fs/namespace.c:3584 [inline]
__x64_sys_mount+0x283/0x300 fs/namespace.c:3584
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x35/0x80 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x6e/0xd8
This happens because of a race condition between:
- The 9p client sending an invalid flush request and later cleaning it up;
- The 9p client in p9_read_work() canceled all pending requests.
Thread 1 Thread 2
...
p9_client_create()
...
p9_fd_create()
...
p9_conn_create()
...
// start Thread 2
INIT_WORK(&m->rq, p9_read_work);
p9_read_work()
...
p9_client_rpc()
...
...
p9_conn_cancel()
...
spin_lock(&m->req_lock);
...
p9_fd_cancelled()
...
...
spin_unlock(&m->req_lock);
// status rewrite
p9_client_cb(m->client, req, REQ_STATUS_ERROR)
// first remove
list_del(&req->req_list);
...
spin_lock(&m->req_lock)
...
// second remove
list_del(&req->req_list);
spin_unlock(&m->req_lock)
...
Commit 74d6a5d56629 ("9p/trans_fd: Fix concurrency del of req_list in
p9_fd_cancelled/p9_read_work") fixes a concurrency issue in the 9p filesystem
client where the req_list could be deleted simultaneously by both
p9_read_work and p9_fd_cancelled functions, but for the case where req->status
equals REQ_STATUS_RCVD.
Update the check for req->status in p9_fd_cancelled to skip processing not
just received requests, but anything that is not SENT, as whatever
changed the state from SENT also removed the request from its list.
Found by Linux Verification Center (linuxtesting.org) with Syzkaller.
[updated the check from status == RECV || status == ERROR to status != SENT]
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (7.8): severity, escalated by confirmed exploitation. This CVE's 7.8 is its impact severity (EG Severity), not escalated.
- EG Severity
- 7.8 HIGHCVSS-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 2026-11-02). 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