CVE-2025-38591 (GCVE-0-2025-38591)

Vulnerability from cvelistv5 – Published: 2025-08-19 17:03 – Updated: 2026-05-11 21:31
VLAI?
Title
bpf: Reject narrower access to pointer ctx fields
Summary
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.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: f96da09473b52c09125cc9bf7d7d4576ae8229e0 , < 7847c4140e06f6e87229faae22cc38525334c156 (git)
Affected: f96da09473b52c09125cc9bf7d7d4576ae8229e0 , < feae34c992eb7191862fb1594c704fbbf650fef8 (git)
Affected: f96da09473b52c09125cc9bf7d7d4576ae8229e0 , < 33660d44e789edb4f303210c813fc56d56377a90 (git)
Affected: f96da09473b52c09125cc9bf7d7d4576ae8229e0 , < 058a0da4f6d916a79b693384111bb80a90d73763 (git)
Affected: f96da09473b52c09125cc9bf7d7d4576ae8229e0 , < 202900ceeef67458c964c2af6e1427c8e533ea7c (git)
Affected: f96da09473b52c09125cc9bf7d7d4576ae8229e0 , < e09299225d5ba3916c91ef70565f7d2187e4cca0 (git)
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Linux Linux Affected: 4.13
Unaffected: 0 , < 4.13 (semver)
Unaffected: 5.10.249 , ≤ 5.10.* (semver)
Unaffected: 5.15.199 , ≤ 5.15.* (semver)
Unaffected: 6.1.162 , ≤ 6.1.* (semver)
Unaffected: 6.12.67 , ≤ 6.12.* (semver)
Unaffected: 6.16.1 , ≤ 6.16.* (semver)
Unaffected: 6.17 , ≤ * (original_commit_for_fix)
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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\u0027t get reported to the mailing list.\"},{\"lang\":\"es\",\"value\":\"En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: bpf: Rechazo de acceso m\u00e1s estrecho a campos de puntero ctx. El siguiente programa BPF, simplificado a partir de una reproducci\u00f3n de syzkaller, genera una advertencia del kernel: r0 = *(u8 *)(r1 + 169); exit; Con el campo de puntero sk en el desplazamiento 168 en __sk_buff. Este acceso se detecta como una lectura m\u00e1s estrecha en bpf_skb_is_valid_access porque no coincide con offsetof(struct __sk_buff, sk). Por lo tanto, se permite y posteriormente procede a bpf_convert_ctx_access. Tenga en cuenta que para el caso \\\"is_narrower_load\\\" en convert_ctx_accesses(), insn-\u0026gt;off est\u00e1 alineado, por lo que cnt puede no ser 0 porque coincide con offsetof(struct __sk_buff, sk) en bpf_convert_ctx_access. Sin embargo, el tama\u00f1o objetivo permanece en 0 y el verificador genera una advertencia del kernel: error del verificador: error durante la conversi\u00f3n de acceso a ctx(1). Este parche corrige este error para devolver un error correcto de \\\"acceso a bpf_context no v\u00e1lido off=X size=Y\\\" en la instrucci\u00f3n de carga. El mismo problema afecta a varios campos en las estructuras de contexto que permiten acceso restringido. Algunos campos no afectados (para sk_msg, sk_lookup y sockopt) tambi\u00e9n se modificaron para usar bpf_ctx_range_ptr por consistencia. Tenga en cuenta que este fallo de syzkaller se report\u00f3 en el enlace \\\"Cierres\\\" a continuaci\u00f3n, que sol\u00eda referirse a un error diferente, corregido en el commit fce7bd8e385a (\\\"bpf/verifier: Handle BPF_LOAD_ACQ instructions in insn_def_regno()\\\"). Debido a que syzbot confundi\u00f3 de alguna manera los dos errores, el nuevo fallo y la reproducci\u00f3n no se reportaron a la lista de correo.\"}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H\",\"baseScore\":5.5,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"NONE\",\"integrityImpact\":\"NONE\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.8,\"impactScore\":3.6}]},\"weaknesses\":[{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"NVD-CWE-noinfo\"}]}],\"configurations\":[{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"4.13\",\"versionEndExcluding\":\"6.16.1\",\"matchCriteriaId\":\"AB2224FC-84B3-4160-8586-B94DC0B0080B\"}]}]}],\"references\":[{\"url\":\"https://git.kernel.org/stable/c/058a0da4f6d916a79b693384111bb80a90d73763\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/202900ceeef67458c964c2af6e1427c8e533ea7c\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/33660d44e789edb4f303210c813fc56d56377a90\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/7847c4140e06f6e87229faae22cc38525334c156\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/e09299225d5ba3916c91ef70565f7d2187e4cca0\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]},{\"url\":\"https://git.kernel.org/stable/c/feae34c992eb7191862fb1594c704fbbf650fef8\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"tags\":[\"Patch\"]}]}}"
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}


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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • 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.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • 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.



Detection rules are retrieved from Rulezet.