Medium [CVE-2026-72423] Guard conntrack opts error writes
This medium-severity Red Hat Linux advisory covers CVE-2026-72423 affecting Red Hat Enterprise Linux 9, Red Hat package: kernel-rt.
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Summary
In the Linux kernel, the following vulnerability has been resolved: bpf: Guard conntrack opts error writes The conntrack lookup and allocation kfuncs take an opts pointer together with an opts__sz argument.
The verifier checks only the memory range described by opts__sz, but the wrappers unconditionally write opts->error whenever the internal lookup or allocation helper returns an error. For an invalid size smaller than the end of opts->error, that write can land outside the verifier-checked range.
Keep returning NULL for invalid arguments, but only report the error through opts->error when the supplied size includes the field. This preserves error reporting for the supported 12-byte and 16-byte layouts, and for other invalid sizes that still include opts->error.
The BPF (Berkeley Packet Filter) subsystem's conntrack (connection tracking) functionality contains an out-of-bounds write vulnerability. This occurs because the system does not properly validate the size of an options structure when reporting errors in conntrack lookup and allocation kernel functions (kfuncs).
An attacker could potentially exploit this by providing an invalid size, leading to memory corruption. Red Hat severity: Moderate — CVSS 5.5 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H).
Weakness: CWE-787. Affected Red Hat products: Red Hat Enterprise Linux 9.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · medium-confidence parse· fetched 24 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · medium-confidence parse· fetched 24 days ago·verify at source
Mitigation
The source record does not include mitigation steps. That is not a statement that no fix exists — read the vendor advisory below for the authoritative guidance.
Official advisory · medium-confidence parse· fetched 24 days ago·verify at source
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