In the Linux kernel, the following vulnerability has been resolved: bpf: check_cond_jmp_op(): properly infer if register is null Nicholas Carlini reported a bug when verifier can incorrectly infer that a pointer is non-null. The bug occurs when two pointers are compared and one of them has a type w/o PTR_MAYBE_NULL flag, but which allows a value to be NULL at runtime. Here is an example: // `a` is PTR_TO_MEM | MEM_RDONLY | PTR_UNTRUSTED // `a` is 0 at runtime. // `b` is PTR_TO_MAP_VALUE | PTR_MAYBE_NULL void *a = bpf_rdonly_cast(0, 0); int *b = bpf_map_lookup_elem(...); if (a == b) *b = 42; // verifier does not catch null pointer dereference This happens because of a special case in check_cond_jmp_op(), which attempts to strip PTR_MAYBE_NULL flags from pointer types, when processing comparisons like `rA == rB`, if either rA or rB can't be null. The non-null property is derived based on the absence of PTR_MAYBE_NULL flag on rA's or rB's type. But that is not sufficient for types like PTR_TO_MEM, as in the example. This patch replaces type_may_be_null() call with reg_not_null(), which contains an allowlist of types for which absence of PTR_MAYBE_NULL actually means that the value can't be NULL at runtime. At the moment, the list in the reg_not_null() omits two types for which PTR_MAYBE_NULL is applicable: PTR_TO_XDP_SOCK and PTR_TO_BUF. In order to remain backward compatible, and assuming that only comparison between pointers of the same type makes sense, this commit extends reg_not_null(). W/o such an extension e.g. verifier_jeq_infer_not_null/null_ptr_to_map_value fails. reg_not_null() can be extended further, but I deem that out of scope for the fix at hand. Explicit base_type(...) != PTR_TO_BTF_ID checks in the check_cond_jmp_op() can be removed with migration to reg_not_null(), but that is a behavioural change, as the special case would start matching for PTR_TO_BTF_ID that is also is_trusted_reg(). I omit the behavioural change from this commit.

There are packages installed that are affected by a vulnerability referenced in the following CVE:

  - In the Linux kernel, the following vulnerability has been resolved: bpf: check_cond_jmp_op(): properly
    infer if register is null Nicholas Carlini reported a bug when verifier can incorrectly infer that a
    pointer is non-null. The bug occurs when two pointers are compared and one of them has a type w/o
    PTR_MAYBE_NULL flag, but which allows a value to be NULL at runtime. Here is an example: // `a` is
    PTR_TO_MEM | MEM_RDONLY | PTR_UNTRUSTED // `a` is 0 at runtime. // `b` is PTR_TO_MAP_VALUE |
    PTR_MAYBE_NULL void *a = bpf_rdonly_cast(0, 0); int *b = bpf_map_lookup_elem(...); if (a == b) *b = 42; //
    verifier does not catch null pointer dereference This happens because of a special case in
    check_cond_jmp_op(), which attempts to strip PTR_MAYBE_NULL flags from pointer types, when processing
    comparisons like `rA == rB`, if either rA or rB can't be null. The non-null property is derived based on
    the absence of PTR_MAYBE_NULL flag on rA's or rB's type. But that is not sufficient for types like
    PTR_TO_MEM, as in the example. This patch replaces type_may_be_null() call with reg_not_null(), which
    contains an allowlist of types for which absence of PTR_MAYBE_NULL actually means that the value can't be
    NULL at runtime. At the moment, the list in the reg_not_null() omits two types for which PTR_MAYBE_NULL is
    applicable: PTR_TO_XDP_SOCK and PTR_TO_BUF. In order to remain backward compatible, and assuming that only
    comparison between pointers of the same type makes sense, this commit extends reg_not_null(). W/o such an
    extension e.g. verifier_jeq_infer_not_null/null_ptr_to_map_value fails. reg_not_null() can be extended
    further, but I deem that out of scope for the fix at hand. Explicit base_type(...) != PTR_TO_BTF_ID checks
    in the check_cond_jmp_op() can be removed with migration to reg_not_null(), but that is a behavioural
    change, as the special case would start matching for PTR_TO_BTF_ID that is also is_trusted_reg(). I omit
    the behavioural change from this commit. (CVE-2026-98134)

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - bpf: check_cond_jmp_op(): properly infer if register is null Nicholas Carlini reported a bug when verifier     can incorrectly infer that a pointer is non-null. The bug occurs when two pointers are compared and one of     them has a type w/o PTR_MAYBE_NULL flag, but which allows a value to be NULL at runtime. Here is an     example: // `a` is PTR_TO_MEM | MEM_RDONLY | PTR_UNTRUSTED // `a` is 0 at runtime. // `b` is     PTR_TO_MAP_VALUE | PTR_MAYBE_NULL void *a = bpf_rdonly_cast(0, 0); int *b = bpf_map_lookup_elem(...); if     (a == b) *b = 42; // verifier does not catch null pointer dereference This happens because of a special     case in check_cond_jmp_op(), which attempts to strip PTR_MAYBE_NULL flags from pointer types, when     processing comparisons like `rA == rB`, if either rA or rB can't be null. The non-null property is derived     based on the absence of PTR_MAYBE_NULL flag on rA's or rB's type. But that is not sufficient for types     like PTR_TO_MEM, as in the example. This patch replaces type_may_be_null() call with reg_not_null(), which     contains an allowlist of types for which absence of PTR_MAYBE_NULL actually means that the value can't be     NULL at runtime. At the moment, the list in the reg_not_null() omits two types for which PTR_MAYBE_NULL is     applicable: PTR_TO_XDP_SOCK and PTR_TO_BUF. In order to remain backward compatible, and assuming that only     comparison between pointers of the same type makes sense, this commit extends reg_not_null(). W/o such an     extension e.g. verifier_jeq_infer_not_null/null_ptr_to_map_value fails. reg_not_null() can be extended     further, but I deem that out of scope for the fix at hand. Explicit base_type(...) != PTR_TO_BTF_ID checks     in the check_cond_jmp_op() can be removed with migration to reg_not_null(), but that is a behavioural     change, as the special case would start matching for PTR_TO_BTF_ID that is also is_trusted_reg(). I omit     the behavioural change from this commit. (CVE-2026-98134)

Note that Nessus relies on the presence of the package as reported by the vendor.

ID	Name	Product	Family	Type	Severity
376443	Ubuntu 24.04 LTS / 26.04 LTS : Linux kernel vulnerabilities (USN-8959-1)	Nessus	Ubuntu Local Security Checks	Local	high
474665	Chainguard: linux-desktop-7.2-bootc: security update to 7.2.7-r0	Tenable Cloud Security	Chainguard Local Security Checks	Local	medium
474665	Chainguard: linux-desktop-7.2-bootc: security update to 7.2.7-r0	Tenable Self-Hosted Container Security	Chainguard Local Security Checks	Local	medium
350590	Linux Distros Unpatched Vulnerability : CVE-2026-98134	Nessus	Misc.	Local	medium

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CVE-2026-98134

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