{"id":"AZL-71033","summary":"CVE-2025-38591 affecting package kernel 5.15.200.1-1","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Reject narrower access to pointer ctx fields\n\nThe following BPF program, simplified from a syzkaller repro, causes a\nkernel warning:\n\n    r0 = *(u8 *)(r1 + 169);\n    exit;\n\nWith pointer field sk being at offset 168 in __sk_buff. This access is\ndetected as a narrower read in bpf_skb_is_valid_access because it\ndoesn't match offsetof(struct __sk_buff, sk). It is therefore allowed\nand later proceeds to bpf_convert_ctx_access. Note that for the\n\"is_narrower_load\" case in the convert_ctx_accesses(), the insn-\u003eoff\nis aligned, so the cnt may not be 0 because it matches the\noffsetof(struct __sk_buff, sk) in the bpf_convert_ctx_access. However,\nthe target_size stays 0 and the verifier errors with a kernel warning:\n\n    verifier bug: error during ctx access conversion(1)\n\nThis patch fixes that to return a proper \"invalid bpf_context access\noff=X size=Y\" error on the load instruction.\n\nThe same issue affects multiple other fields in context structures that\nallow narrow access. Some other non-affected fields (for sk_msg,\nsk_lookup, and sockopt) were also changed to use bpf_ctx_range_ptr for\nconsistency.\n\nNote this syzkaller crash was reported in the \"Closes\" link below, which\nused to be about a different bug, fixed in\ncommit fce7bd8e385a (\"bpf/verifier: Handle BPF_LOAD_ACQ instructions\nin insn_def_regno()\"). Because syzbot somehow confused the two bugs,\nthe new crash and repro didn't get reported to the mailing list.","modified":"2026-04-01T05:22:30.186040Z","published":"2025-08-19T17:15:36Z","upstream":["CVE-2025-38591"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-38591"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:2","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"5.15.200.1-1"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-71033.json"}}],"schema_version":"1.7.5"}