{"id":"CVE-2026-45886","state":"PUBLISHED","title":"bpf: Fix bpf_xdp_store_bytes proto for read-only arg","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix bpf_xdp_store_bytes proto for read-only arg\n\nWhile making some maps in Cilium read-only from the BPF side, we noticed\nthat the bpf_xdp_store_bytes proto is incorrect. In particular, the\nverifier was throwing the following error:\n\n  ; ret = ctx_store_bytes(ctx, l3_off + offsetof(struct iphdr, saddr),\n                          &nat->address, 4, 0);\n  635: (79) r1 = *(u64 *)(r10 -144)     ; R1=ctx() R10=fp0 fp-144=ctx()\n  636: (b4) w2 = 26                     ; R2=26\n  637: (b4) w4 = 4                      ; R4=4\n  638: (b4) w5 = 0                      ; R5=0\n  639: (85) call bpf_xdp_store_bytes#190\n  write into map forbidden, value_size=6 off=0 size=4\n\nnat comes from a BPF_F_RDONLY_PROG map, so R3 is a PTR_TO_MAP_VALUE.\nThe verifier checks the helper's memory access to R3 in\ncheck_mem_size_reg, as it reaches ARG_CONST_SIZE argument. The third\nargument has expected type ARG_PTR_TO_UNINIT_MEM, which includes the\nMEM_WRITE flag. The verifier thus checks for a BPF_WRITE access on R3.\nGiven R3 points to a read-only map, the check fails.\n\nConversely, ARG_PTR_TO_UNINIT_MEM can also lead to the helper reading\nfrom uninitialized memory.\n\nThis patch simply fixes the expected argument type to match that of\nbpf_skb_store_bytes.","publishedAt":"2026-05-27T12:16:58.000Z","updatedAt":"2026-05-27T12:16:58.000Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"3f364222d032eea6b245780e845ad213dab28cdd","status":"affected","lessThan":"ffb5d1c5e3933b947fc7303ad68bf0c536d0c85e","versionType":"git"},{"version":"3f364222d032eea6b245780e845ad213dab28cdd","status":"affected","lessThan":"ddc34a1b85505c919026ddc82fafdada9a160b15","versionType":"git"},{"version":"3f364222d032eea6b245780e845ad213dab28cdd","status":"affected","lessThan":"0db169a91381a473b7974021d1c02f8da72c5775","versionType":"git"},{"version":"3f364222d032eea6b245780e845ad213dab28cdd","status":"affected","lessThan":"d7b87adeb0eb539b9b824b101bb14fb01e41240b","versionType":"git"},{"version":"3f364222d032eea6b245780e845ad213dab28cdd","status":"affected","lessThan":"57f7f6a0ad04a65c8a7a067b2f56cbbf2aec9e52","versionType":"git"},{"version":"3f364222d032eea6b245780e845ad213dab28cdd","status":"affected","lessThan":"6557f1565d779851c4db9c488c49c05a47a6e72f","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/core/filter.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.18","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.18","versionType":"semver"},{"version":"6.1.165","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.128","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.75","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.14","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.4","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/core/filter.c"]}],"references":["https://git.kernel.org/stable/c/ffb5d1c5e3933b947fc7303ad68bf0c536d0c85e","https://git.kernel.org/stable/c/ddc34a1b85505c919026ddc82fafdada9a160b15","https://git.kernel.org/stable/c/0db169a91381a473b7974021d1c02f8da72c5775","https://git.kernel.org/stable/c/d7b87adeb0eb539b9b824b101bb14fb01e41240b","https://git.kernel.org/stable/c/57f7f6a0ad04a65c8a7a067b2f56cbbf2aec9e52","https://git.kernel.org/stable/c/6557f1565d779851c4db9c488c49c05a47a6e72f"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:07.131Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/45xxx/CVE-2026-45886.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-45886","state":"PUBLISHED","datePublished":"2026-05-27T12:16:58.000Z","dateUpdated":"2026-05-27T12:16:58.000Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-05-13T15:03:33.082Z"},"containers":{"cna":{"title":"bpf: Fix bpf_xdp_store_bytes proto for read-only arg","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix bpf_xdp_store_bytes proto for read-only arg\n\nWhile making some maps in Cilium read-only from the BPF side, we noticed\nthat the bpf_xdp_store_bytes proto is incorrect. In particular, the\nverifier was throwing the following error:\n\n  ; ret = ctx_store_bytes(ctx, l3_off + offsetof(struct iphdr, saddr),\n                          &nat->address, 4, 0);\n  635: (79) r1 = *(u64 *)(r10 -144)     ; R1=ctx() R10=fp0 fp-144=ctx()\n  636: (b4) w2 = 26                     ; R2=26\n  637: (b4) w4 = 4                      ; R4=4\n  638: (b4) w5 = 0                      ; R5=0\n  639: (85) call bpf_xdp_store_bytes#190\n  write into map forbidden, value_size=6 off=0 size=4\n\nnat comes from a BPF_F_RDONLY_PROG map, so R3 is a PTR_TO_MAP_VALUE.\nThe verifier checks the helper's memory access to R3 in\ncheck_mem_size_reg, as it reaches ARG_CONST_SIZE argument. The third\nargument has expected type ARG_PTR_TO_UNINIT_MEM, which includes the\nMEM_WRITE flag. The verifier thus checks for a BPF_WRITE access on R3.\nGiven R3 points to a read-only map, the check fails.\n\nConversely, ARG_PTR_TO_UNINIT_MEM can also lead to the helper reading\nfrom uninitialized memory.\n\nThis patch simply fixes the expected argument type to match that of\nbpf_skb_store_bytes."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"3f364222d032eea6b245780e845ad213dab28cdd","status":"affected","lessThan":"ffb5d1c5e3933b947fc7303ad68bf0c536d0c85e","versionType":"git"},{"version":"3f364222d032eea6b245780e845ad213dab28cdd","status":"affected","lessThan":"ddc34a1b85505c919026ddc82fafdada9a160b15","versionType":"git"},{"version":"3f364222d032eea6b245780e845ad213dab28cdd","status":"affected","lessThan":"0db169a91381a473b7974021d1c02f8da72c5775","versionType":"git"},{"version":"3f364222d032eea6b245780e845ad213dab28cdd","status":"affected","lessThan":"d7b87adeb0eb539b9b824b101bb14fb01e41240b","versionType":"git"},{"version":"3f364222d032eea6b245780e845ad213dab28cdd","status":"affected","lessThan":"57f7f6a0ad04a65c8a7a067b2f56cbbf2aec9e52","versionType":"git"},{"version":"3f364222d032eea6b245780e845ad213dab28cdd","status":"affected","lessThan":"6557f1565d779851c4db9c488c49c05a47a6e72f","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/core/filter.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.18","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.18","versionType":"semver"},{"version":"6.1.165","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.128","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.75","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.14","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.4","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/core/filter.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/ffb5d1c5e3933b947fc7303ad68bf0c536d0c85e"},{"url":"https://git.kernel.org/stable/c/ddc34a1b85505c919026ddc82fafdada9a160b15"},{"url":"https://git.kernel.org/stable/c/0db169a91381a473b7974021d1c02f8da72c5775"},{"url":"https://git.kernel.org/stable/c/d7b87adeb0eb539b9b824b101bb14fb01e41240b"},{"url":"https://git.kernel.org/stable/c/57f7f6a0ad04a65c8a7a067b2f56cbbf2aec9e52"},{"url":"https://git.kernel.org/stable/c/6557f1565d779851c4db9c488c49c05a47a6e72f"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-05-27T12:16:58.000Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.18","versionEndExcluding":"6.1.165"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.18","versionEndExcluding":"6.6.128"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.18","versionEndExcluding":"6.12.75"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.18","versionEndExcluding":"6.18.14"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.18","versionEndExcluding":"6.19.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.18","versionEndExcluding":"7.0"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}