Linux: Out-of-bounds Read
CVE-2026-63992 is a critical-severity out-of-bounds read vulnerability in Linux, with a CVSS 3.1 base score of 9.1 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 5a92cb45e34749865d03daf8d3500f77b5f6644c, c7b7ec3e69e673c0d6b57f74d21da50c485c598e, 7f4f7efe7f30edd29c4988de01728bf2398217e4 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 0.51% 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 5a92cb45e34749865d03daf8d3500f77b5f6644c or c7b7ec3e69e673c0d6b57f74d21da50c485c598e or 7f4f7efe7f30edd29c4988de01728bf2398217e4 or e917d0c69f01af2bb4fbea2b66d560a53b3ac7ec, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.10.259 or 5.15.210 or 6.1.176 or 6.6.143, 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 | 4cb47a8644cc9eb8ec81190a50e79e6530d0297f up to, but not including, 5a92cb45e34749865d03daf8d3500f77b5f6644c; 4cb47a8644cc9eb8ec81190a50e79e6530d0297f up to, but not including, c7b7ec3e69e673c0d6b57f74d21da50c485c598e; 4cb47a8644cc9eb8ec81190a50e79e6530d0297f up to, but not including, 7f4f7efe7f30edd29c4988de01728bf2398217e4; 4cb47a8644cc9eb8ec81190a50e79e6530d0297f up to, but not including, e917d0c69f01af2bb4fbea2b66d560a53b3ac7ec; 4cb47a8644cc9eb8ec81190a50e79e6530d0297f up to, but not including, a096b6e34f602950af9a2b0856cd93a5f4c276d7; 4cb47a8644cc9eb8ec81190a50e79e6530d0297f up to, but not including, 43368636c663cff6e59dde93cf4b8e43ac28eb93; 4cb47a8644cc9eb8ec81190a50e79e6530d0297f up to, but not including, cb549df9ce4ee15c9d5b19ddab12cf2128e4313c; 4cb47a8644cc9eb8ec81190a50e79e6530d0297f up to, but not including, 509323077ef79a26ba0c60bb556e45c12c398b2d; and 1 more ranges | 5a92cb45e34749865d03daf8d3500f77b5f6644c, c7b7ec3e69e673c0d6b57f74d21da50c485c598e, 7f4f7efe7f30edd29c4988de01728bf2398217e4, e917d0c69f01af2bb4fbea2b66d560a53b3ac7ec, a096b6e34f602950af9a2b0856cd93a5f4c276d7, 43368636c663cff6e59dde93cf4b8e43ac28eb93 |
| Linux | Linux Kernel | 5.9 up to, but not including, 5.10.259; 5.11 up to, but not including, 5.15.210; 5.16 up to, but not including, 6.1.176; 6.2 up to, but not including, 6.6.143; 6.7 up to, but not including, 6.12.93; 6.13 up to, but not including, 6.18.35; 6.19 up to, but not including, 7.0.12; 7.1 | 5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.93, 6.18.35 |
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
- NoneNothing can be modified.
- 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:N/A:H. Scored by CNA.
Official description
In the Linux kernel, the following vulnerability has been resolved: tunnels: do not assume transport header in iptunnel_pmtud_check_icmp() In some cases, iptunnel_pmtud_check_icmp() can be called while skb transport header is not set. This triggers an out-of-bound access, because (typeof(skb->transport_header))~0U is 65535. Access the icmp header based on IPv4 network header, after making sure icmp->type is present in skb linear part. Note that iptunnel_pmtud_check_icmpv6()) is fine.
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/43368636c663cff6e59dde93cf4b8e43ac28eb93
- git.kernel.org/stable/c/509323077ef79a26ba0c60bb556e45c12c398b2d
- git.kernel.org/stable/c/5a92cb45e34749865d03daf8d3500f77b5f6644c
- git.kernel.org/stable/c/7f4f7efe7f30edd29c4988de01728bf2398217e4
- git.kernel.org/stable/c/a096b6e34f602950af9a2b0856cd93a5f4c276d7
- git.kernel.org/stable/c/c7b7ec3e69e673c0d6b57f74d21da50c485c598e
- git.kernel.org/stable/c/cb549df9ce4ee15c9d5b19ddab12cf2128e4313c
- git.kernel.org/stable/c/e917d0c69f01af2bb4fbea2b66d560a53b3ac7ec
Recent Out-of-bounds Read vulnerabilities
- 7.1 High severity
- 7.8 High severity
- 7.3 High severity
- 7.1 High severity
- 7.8 High severity
- 9.8 Critical severity
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