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Back to active CVEs
High ยท CVSS 7.8CVE-2026-31700

net/packet: fix TOCTOU race on mmap'd vnet_hdr in tpacket_snd()CVE-2026-31700

Answer in brief

CVE-2026-31700 records a High severity (CVSS 7.8) vulnerability in net/packet: fix TOCTOU race on mmap'd vnet_hdr in tpacket_snd(). The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic) and additional mapped packages. Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published May 1, 2026Updated Oct 19, 2026Source checked Nov 4, 2026First seen by HOL Jun 19, 2026Material review Oct 19, 2026
Upstream Advisory

Key facts

Risk
High ยท CVSS 7.8
Exploitation
Not marked as known exploited
Affected software
12 mapped packages or products
Fix availability
Available

Why this deserves its current priority

CVSS is 7.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Linux/Linux (generic), Linux/Linux (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic), Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (generic) and additional mapped packages. Check affected ranges and fixed versions before updating.

Affected products and reported versions
ProductAffected versionsFixed versions
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*Not reportedNot reported
cpe:2.3:o:linux:linux_kernel:7.1:rc1:*:*:*:*:*:*Not reportedNot reported
cpe:2.3:o:linux:linux_kernel:7.1:rc2:*:*:*:*:*:*Not reportedNot reported
Mapped affected packages and fixed versions
PackageAffected rangeFixed version
Linux/Linuxgeneric>=1d036d25e5609ba73fee6a88db01c306b140d512 <0f4c9754956b86de158a4af5278c5cf5bda9439e || >=1d036d25e5609ba73fee6a88db01c306b140d512 <714aa973da8163925eda7efd49361ccbee21ee46 || >=1d036d25e5609ba73fee6a88db01c306b140d512 <1490f82353bdabc09265a74e645b07f05cf4188e || >=1d036d25e5609ba73fee6a88db01c306b140d512 <74e2db36fe50e3ad9d5300d7fd0e6e2a15a6d121 || >=1d036d25e5609ba73fee6a88db01c306b140d512 <3a1bf9116ea31470b89692585c3910dfe830dcdd || >=1d036d25e5609ba73fee6a88db01c306b140d512 <28324a3b62d9ce7f9bdd65a8ce63f382041d1b27 || >=1d036d25e5609ba73fee6a88db01c306b140d512 <48a6ef291a17639e1b6ae0fbe9c8b2bb87d7804b || >=1d036d25e5609ba73fee6a88db01c306b140d512 <2c054e17d9d41f1020376806c7f750834ced4dc50f4c9754956b86de158a4af5278c5cf5bda9439e, 714aa973da8163925eda7efd49361ccbee21ee46, 1490f82353bdabc09265a74e645b07f05cf4188e, 74e2db36fe50e3ad9d5300d7fd0e6e2a15a6d121, 3a1bf9116ea31470b89692585c3910dfe830dcdd, 28324a3b62d9ce7f9bdd65a8ce63f382041d1b27, 48a6ef291a17639e1b6ae0fbe9c8b2bb87d7804b, 2c054e17d9d41f1020376806c7f750834ced4dc5
Linux/Linuxgeneric4.6Not reported
Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFPgeneric>=V3.1.6 <**
Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFPgeneric>=V3.1.7 <**
Siemens/SIMATIC S7-1500 CPU 1518F-4 PN/DP MFPgeneric>=V3.1.6 <**
Siemens/SIMATIC S7-1500 CPU 1518F-4 PN/DP MFPgeneric>=V3.1.7 <**
Siemens/SIMATIC S7-1500 TM MFP - GNU/Linux subsystemgeneric>=0 <**
Siemens/SIPLUS S7-1500 CPU 1518-4 PN/DP MFPgeneric>=V3.1.6 <**
Siemens/SIPLUS S7-1500 CPU 1518-4 PN/DP MFPgeneric>=V3.1.7 <**

Recommended response

  1. 1Check inventory. Check lockfiles and deployed manifests for Linux/Linux, Linux/Linux, Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP.
  2. 2Review the reported fix. Update Linux/Linux to 0f4c9754956b86de158a4af5278c5cf5bda9439e; Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP to *; Siemens/SIMATIC S7-1500 CPU 1518-4 PN/DP MFP to *; Siemens/SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP to *; Siemens/SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP to *; Siemens/SIMATIC S7-1500 TM MFP - GNU/Linux subsystem to *; Siemens/SIPLUS S7-1500 CPU 1518-4 PN/DP MFP to *; Siemens/SIPLUS S7-1500 CPU 1518-4 PN/DP MFP to * if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

  1. Published upstream

    May 1, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  2. Source modified

    Oct 19, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  3. First seen by HOL

    Jun 19, 2026

Sources and claim methodology

  • Source referencecert-portal.siemens.com
  • Source referencecert-portal.siemens.com
  • Source referencecert-portal.siemens.com
  • Source referencegit.kernel.org
  • Source referencegit.kernel.org
  • Source referencegit.kernel.org
  • Source referencegit.kernel.org
  • Source referencegit.kernel.org
  • Source referencegit.kernel.org
  • Source referencegit.kernel.org
  • Source referencegit.kernel.org
Upstream source 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.

Quoted source text, attributed separately from HOL analysis.

Record context

Vulnerability class
Vulnerability
EPSS
Not reported
CWE IDs
CWE-362, CWE-367
Source
CVE List V5
Source checked
Nov 4, 2026
References
11 linked sources
Open source record