cbcvebase.
CVE-2025-38591
published 2025-08-19

CVE-2025-38591: In the Linux kernel, the following vulnerability has been resolved: bpf: Reject narrower access to pointer ctx fields The following BPF program, simplified…

PriorityP420medium5.5CVSS 3.1
AVLACLPRLUINSUCNINAH
EPSS
0.19%
9.2th percentile
In the Linux kernel, the following vulnerability has been resolved: bpf: Reject narrower access to pointer ctx fields The following BPF program, simplified from a syzkaller repro, causes a kernel warning: r0 = *(u8 *)(r1 + 169); exit; With pointer field sk being at offset 168 in __sk_buff. This access is detected as a narrower read in bpf_skb_is_valid_access because it doesn't match offsetof(struct __sk_buff, sk). It is therefore allowed and later proceeds to bpf_convert_ctx_access. Note that for the "is_narrower_load" case in the convert_ctx_accesses(), the insn->off is aligned, so the cnt may not be 0 because it matches the offsetof(struct __sk_buff, sk) in the bpf_convert_ctx_access. However, the target_size stays 0 and the verifier errors with a kernel warning: verifier bug: error during ctx access conversion(1) This patch fixes that to return a proper "invalid bpf_context access off=X size=Y" error on the load instruction. The same issue affects multiple other fields in context structures that allow narrow access. Some other non-affected fields (for sk_msg, sk_lookup, and sockopt) were also changed to use bpf_ctx_range_ptr for consistency. Note this syzkaller crash was reported in the "Closes" link below, which used to be about a different bug, fixed in commit fce7bd8e385a ("bpf/verifier: Handle BPF_LOAD_ACQ instructions in insn_def_regno()"). Because syzbot somehow confused the two bugs, the new crash and repro didn't get reported to the mailing list.

Affected

62 ranges· showing 25
VendorProductVersion rangeFixed in
debianlinux< linux 6.1.162-1 (bookworm)linux 6.1.162-1 (bookworm)
debianlinux-6.1< linux 6.1.162-1 (bookworm)linux 6.1.162-1 (bookworm)
linuxlinux
linuxlinux>= f96da09473b52c09125cc9bf7d7d4576ae8229e0 < 7847c4140e06f6e87229faae22cc38525334c1567847c4140e06f6e87229faae22cc38525334c156
linuxlinux>= f96da09473b52c09125cc9bf7d7d4576ae8229e0 < feae34c992eb7191862fb1594c704fbbf650fef8feae34c992eb7191862fb1594c704fbbf650fef8
linuxlinux>= f96da09473b52c09125cc9bf7d7d4576ae8229e0 < 33660d44e789edb4f303210c813fc56d56377a9033660d44e789edb4f303210c813fc56d56377a90
linuxlinux>= f96da09473b52c09125cc9bf7d7d4576ae8229e0 < 058a0da4f6d916a79b693384111bb80a90d73763058a0da4f6d916a79b693384111bb80a90d73763
linuxlinux>= f96da09473b52c09125cc9bf7d7d4576ae8229e0 < 202900ceeef67458c964c2af6e1427c8e533ea7c202900ceeef67458c964c2af6e1427c8e533ea7c
linuxlinux>= f96da09473b52c09125cc9bf7d7d4576ae8229e0 < e09299225d5ba3916c91ef70565f7d2187e4cca0e09299225d5ba3916c91ef70565f7d2187e4cca0
linuxlinux_kernel>= 0 < 5.10.249-15.10.249-1
linuxlinux_kernel>= 0 < 6.1.162-16.1.162-1
linuxlinux_kernel>= 0 < 6.12.69-16.12.69-1
linuxlinux_kernel>= 0 < 6.16.3-16.16.3-1
linuxlinux_kernel>= 4.13 < 6.16.16.16.1
msrcazl3_kernel_6.6.104.2-4_on_azure_linux_3.0
msrcazl3_kernel_6.6.112.1-2_on_azure_linux_3.0
msrcazl3_kernel_6.6.117.1-1_on_azure_linux_3.0
msrcazl3_kernel_6.6.119.3-1_on_azure_linux_3.0
msrcazl3_kernel_6.6.119.3-3_on_azure_linux_3.0
msrcazl3_kernel_6.6.121.1-1_on_azure_linux_3.0
msrcazl3_kernel_6.6.126.1-1_on_azure_linux_3.0
msrcazl3_kernel_6.6.130.1-3_on_azure_linux_3.0
msrcazl3_kernel_6.6.96.2-1_on_azure_linux_3.0
msrcazl3_kernel_6.6.96.2-2_on_azure_linux_3.0
msrccbl2_kernel_5.15.186.1-1_on_cbl_mariner_2.0

CVSS provenance

nvdv3.15.5MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
osv5.5MEDIUM
vendor_ubuntu7.8HIGH
vendor_debian5.5MEDIUM
vendor_msrc5.5MEDIUM
vendor_redhat5.5MEDIUM
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