CVE-2026-31700
Essential information
- Published
- 01/05/2026 14:16
- Modified
- 01/05/2026 15:24
- Author
- —
- Creator
- —
- CVSS
- 7.8 HIGH (v3.1)
- CISA KEV
- No
- CWE
- CWE-362
- CVSS vector
-
—
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H—
CVSS metrics
- Access vector
- —
- Access complexity
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- Authentication
- —
- Confidentiality impact
- —
- Integrity impact
- —
- Availability impact
- —
- Exploitability
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- Remediation level
- —
- Report confidence
- —
- Temporal score
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- Attack vector
- LOCAL
- Attack complexity
- LOW
- Privileges required
- LOW
- User interaction
- NONE
- Scope
- UNCHANGED
- Confidentiality impact
- HIGH
- Integrity impact
- HIGH
- Availability impact
- HIGH
- Exploit code maturity
- —
- Remediation level
- —
- Report confidence
- —
- Temporal score
- —
- Attack vector
- —
- Attack complexity
- —
- Attack requirements
- —
- Privileges required
- —
- User interaction
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- Confidentiality (V)
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- Confidentiality (S)
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- Integrity (V)
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- Integrity (S)
- —
- Availability (V)
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- Availability (S)
- —
- Exploit maturity
- —
Description
In the Linux kernel, the following vulnerability has been resolved:
net/packet: fix TOCTOU race on mmap'd vnet_hdr in tpacket_snd()
In tpacket_snd(), when PACKET_VNET_HDR is enabled, vnet_hdr points
directly into the mmap'd TX ring buffer shared with userspace. The
kernel validates the header via __packet_snd_vnet_parse() but then
re-reads all fields later in virtio_net_hdr_to_skb(). A concurrent
userspace thread can modify the vnet_hdr fields between validation
and use, bypassing all safety checks.
The non-TPACKET path (packet_snd()) already correctly copies vnet_hdr
to a stack-local variable. All other vnet_hdr consumers in the kernel
(tun.c, tap.c, virtio_net.c) also use stack copies. The TPACKET TX
path is the only caller of virtio_net_hdr_to_skb() that reads directly
from user-controlled shared memory.
Fix this by copying vnet_hdr from the mmap'd ring buffer to a
stack-local variable before validation and use, consistent with the
approach used in packet_snd() and all other callers.
NVD status
- Status
- Modified — CVE has been recently published to the CVE List and has been received by the NVD.
- Source
- nist-nvd-api
- NVD
- View on NVD
Affected products (CPE)
| Product | CPE |
|---|---|
| linux / linux kernel | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| linux / linux kernel | cpe:2.3:o:linux:linux_kernel:7.1:rc1:*:*:*:*:*:* |
| linux / linux kernel | cpe:2.3:o:linux:linux_kernel:7.1:rc2:*:*:*:*:*:* |