CVE-2026-45886 (GCVE-0-2026-45886)

Vulnerability from cvelistv5 – Published: 2026-05-27 12:16 – Updated: 2026-05-27 12:16
VLAI?
Title
bpf: Fix bpf_xdp_store_bytes proto for read-only arg
Summary
In the Linux kernel, the following vulnerability has been resolved: bpf: Fix bpf_xdp_store_bytes proto for read-only arg While making some maps in Cilium read-only from the BPF side, we noticed that the bpf_xdp_store_bytes proto is incorrect. In particular, the verifier was throwing the following error: ; ret = ctx_store_bytes(ctx, l3_off + offsetof(struct iphdr, saddr), &nat->address, 4, 0); 635: (79) r1 = *(u64 *)(r10 -144) ; R1=ctx() R10=fp0 fp-144=ctx() 636: (b4) w2 = 26 ; R2=26 637: (b4) w4 = 4 ; R4=4 638: (b4) w5 = 0 ; R5=0 639: (85) call bpf_xdp_store_bytes#190 write into map forbidden, value_size=6 off=0 size=4 nat comes from a BPF_F_RDONLY_PROG map, so R3 is a PTR_TO_MAP_VALUE. The verifier checks the helper's memory access to R3 in check_mem_size_reg, as it reaches ARG_CONST_SIZE argument. The third argument has expected type ARG_PTR_TO_UNINIT_MEM, which includes the MEM_WRITE flag. The verifier thus checks for a BPF_WRITE access on R3. Given R3 points to a read-only map, the check fails. Conversely, ARG_PTR_TO_UNINIT_MEM can also lead to the helper reading from uninitialized memory. This patch simply fixes the expected argument type to match that of bpf_skb_store_bytes.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 3f364222d032eea6b245780e845ad213dab28cdd , < ffb5d1c5e3933b947fc7303ad68bf0c536d0c85e (git)
Affected: 3f364222d032eea6b245780e845ad213dab28cdd , < ddc34a1b85505c919026ddc82fafdada9a160b15 (git)
Affected: 3f364222d032eea6b245780e845ad213dab28cdd , < 0db169a91381a473b7974021d1c02f8da72c5775 (git)
Affected: 3f364222d032eea6b245780e845ad213dab28cdd , < d7b87adeb0eb539b9b824b101bb14fb01e41240b (git)
Affected: 3f364222d032eea6b245780e845ad213dab28cdd , < 57f7f6a0ad04a65c8a7a067b2f56cbbf2aec9e52 (git)
Affected: 3f364222d032eea6b245780e845ad213dab28cdd , < 6557f1565d779851c4db9c488c49c05a47a6e72f (git)
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    Linux Linux Affected: 5.18
Unaffected: 0 , < 5.18 (semver)
Unaffected: 6.1.165 , ≤ 6.1.* (semver)
Unaffected: 6.6.128 , ≤ 6.6.* (semver)
Unaffected: 6.12.75 , ≤ 6.12.* (semver)
Unaffected: 6.18.14 , ≤ 6.18.* (semver)
Unaffected: 6.19.4 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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{
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      "cpeApplicability": [
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      "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                          \u0026nat-\u003eaddress, 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\u0027s 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."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-27T12:16:58.000Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/ffb5d1c5e3933b947fc7303ad68bf0c536d0c85e"
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          "url": "https://git.kernel.org/stable/c/ddc34a1b85505c919026ddc82fafdada9a160b15"
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          "url": "https://git.kernel.org/stable/c/6557f1565d779851c4db9c488c49c05a47a6e72f"
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      "title": "bpf: Fix bpf_xdp_store_bytes proto for read-only arg",
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    "cveId": "CVE-2026-45886",
    "datePublished": "2026-05-27T12:16:58.000Z",
    "dateReserved": "2026-05-13T15:03:33.082Z",
    "dateUpdated": "2026-05-27T12:16:58.000Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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