Linux: Out-of-bounds Read
CVE-2026-31685 is a critical-severity out-of-bounds read vulnerability in Linux, with a CVSS 3.1 base score of 9.4 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 4d75bc2cd093bf5803edf512c099bfb220fd6459, 7d6a57411caf54df025860c9b1a82cd42d57a562, d5603591373441fecf9951833d6d873e09320f08 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.48% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Linux to 4d75bc2cd093bf5803edf512c099bfb220fd6459 or 7d6a57411caf54df025860c9b1a82cd42d57a562 or d5603591373441fecf9951833d6d873e09320f08 or 288138418bef956f8b295751a4536c60f0e89f4a, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.6.136 or 6.12.83 or 6.18.24 or 6.19.14, whichever matches your release line, or a later version.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 4d75bc2cd093bf5803edf512c099bfb220fd6459; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 7d6a57411caf54df025860c9b1a82cd42d57a562; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, d5603591373441fecf9951833d6d873e09320f08; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 288138418bef956f8b295751a4536c60f0e89f4a; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 9eda5478746ef7dc0e4e537b5a5e4b0ca1027091; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 807d6ee15804df6f01a35c910f09612e858739a6; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 309ae3e9a51a69699ca94eac5fac5688fa562d55; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, fdce0b3590f724540795b874b4c8850c90e6b0a8; and 1 more ranges | 4d75bc2cd093bf5803edf512c099bfb220fd6459, 7d6a57411caf54df025860c9b1a82cd42d57a562, d5603591373441fecf9951833d6d873e09320f08, 288138418bef956f8b295751a4536c60f0e89f4a, 9eda5478746ef7dc0e4e537b5a5e4b0ca1027091, 807d6ee15804df6f01a35c910f09612e858739a6 |
| Siemens | SIMATIC S7-1500 TM MFP - GNU/Linux subsystem | all versions | Not stated |
| Linux | Linux Kernel | 2.6.12.1 up to, but not including, 6.6.136; 6.7 up to, but not including, 6.12.83; 6.13 up to, but not including, 6.18.24; 6.19 up to, but not including, 6.19.14; 2.6.12; 7.0 | 6.6.136, 6.12.83, 6.18.24, 6.19.14 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- LowLimited modification of data is possible.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:H. Scored by CNA.
Official description
In the Linux kernel, the following vulnerability has been resolved: netfilter: ip6t_eui64: reject invalid MAC header for all packets `eui64_mt6()` derives a modified EUI-64 from the Ethernet source address and compares it with the low 64 bits of the IPv6 source address. The existing guard only rejects an invalid MAC header when `par->fragoff != 0`. For packets with `par->fragoff == 0`, `eui64_mt6()` can still reach `eth_hdr(skb)` even when the MAC header is not valid. Fix this by removing the `par->fragoff != 0` condition so that packets with an invalid MAC header are rejected before accessing `eth_hdr(skb)`.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Out-of-bounds Read
The product reads data past the end, or before the beginning, of the intended buffer.
How developers prevent this class of flaw
- Use a language that provides appropriate memory abstractions.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/288138418bef956f8b295751a4536c60f0e89f4a
- git.kernel.org/stable/c/309ae3e9a51a69699ca94eac5fac5688fa562d55
- git.kernel.org/stable/c/807d6ee15804df6f01a35c910f09612e858739a6
- git.kernel.org/stable/c/9eda5478746ef7dc0e4e537b5a5e4b0ca1027091
- git.kernel.org/stable/c/fdce0b3590f724540795b874b4c8850c90e6b0a8
Other references
Recent Out-of-bounds Read vulnerabilities
- 9.1 Critical severity
- 7.8 High severity
- 7.1 High severity
- 7.5 High severity
- 7.5 High severity
- 9.1 Critical severity
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