CVE-2026-68458 (GCVE-0-2026-68458)

Vulnerability from cvelistv5 – Published: 2026-08-15 05:51 – Updated: 2026-08-17 05:39
VLAI
Title
binder: cache secctx size before release zeroes it
Summary
In the Linux kernel, the following vulnerability has been resolved: binder: cache secctx size before release zeroes it binder_transaction() bounds the scatter-gather buffer area with sg_buf_end_offset and subtracts the aligned LSM context size because the secctx is written at the tail of that area. The subtraction reads lsmctx.len, but that field has already been cleared by the time the line runs: security_secid_to_secctx(secid, &lsmctx) /* lsmctx.len set */ lsmctx_aligned_size = ALIGN(lsmctx.len, sizeof(u64)) extra_buffers_size += lsmctx_aligned_size ... security_release_secctx(&lsmctx) /* memset zeroes len */ ... sg_buf_end_offset = sg_buf_offset + extra_buffers_size - ALIGN(lsmctx.len, sizeof(u64)) /* ALIGN(0,8) */ security_release_secctx() does memset(cp, 0, sizeof(*cp)), so lsmctx.len reads back as 0 and the subtraction contributes nothing, leaving sg_buf_end_offset too large by the aligned secctx size on every transaction to a txn_security_ctx node. Each BINDER_TYPE_PTR object then derives buf_left = sg_buf_end_offset - sg_buf_offset as the sole upper bound on its copy, so the inflated end offset lets the copy run into the bytes that already hold the secctx. The aligned size must therefore be cached before release rather than re-read from the now-cleared field. Fix by caching it in lsmctx_aligned_size at function scope when it is first computed and subtracting lsmctx_aligned_size instead of re-reading lsmctx.len after release. Reuse the same value for the earlier buf_offset computation.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 6fba89813ccf333d2bc4d5caea04cd5f3c39eb50 , < 1228926e1e4d605cc74d9e675558982a6f2cf446 (git)
Affected: 6fba89813ccf333d2bc4d5caea04cd5f3c39eb50 , < 4257f45ee1fddd0558e77b62af8bb63fd87b2162 (git)
Affected: 6fba89813ccf333d2bc4d5caea04cd5f3c39eb50 , < b34826e55aad3520ec813f1f367c11b24b29dc9f (git)
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Linux Linux Affected: 6.14
Unaffected: 0 , < 6.14 (semver)
Unaffected: 6.18.40 , ≤ 6.18.* (semver)
Unaffected: 7.1.5 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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{
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          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/android/binder.c"
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbinder: cache secctx size before release zeroes it\n\nbinder_transaction() bounds the scatter-gather buffer area with\nsg_buf_end_offset and subtracts the aligned LSM context size because\nthe secctx is written at the tail of that area.  The subtraction reads\nlsmctx.len, but that field has already been cleared by the time the\nline runs:\n\n    security_secid_to_secctx(secid, \u0026lsmctx)   /* lsmctx.len set */\n    lsmctx_aligned_size = ALIGN(lsmctx.len, sizeof(u64))\n    extra_buffers_size += lsmctx_aligned_size\n    ...\n    security_release_secctx(\u0026lsmctx)            /* memset zeroes len */\n    ...\n    sg_buf_end_offset = sg_buf_offset + extra_buffers_size\n                        - ALIGN(lsmctx.len, sizeof(u64)) /* ALIGN(0,8) */\n\nsecurity_release_secctx() does memset(cp, 0, sizeof(*cp)), so lsmctx.len\nreads back as 0 and the subtraction contributes nothing, leaving\nsg_buf_end_offset too large by the aligned secctx size on every\ntransaction to a txn_security_ctx node.\n\nEach BINDER_TYPE_PTR object then derives buf_left = sg_buf_end_offset -\nsg_buf_offset as the sole upper bound on its copy, so the inflated end\noffset lets the copy run into the bytes that already hold the secctx.\n\nThe aligned size must therefore be cached before release rather than\nre-read from the now-cleared field.  Fix by caching it in\nlsmctx_aligned_size at function scope when it is first computed and\nsubtracting lsmctx_aligned_size instead of re-reading lsmctx.len after\nrelease.  Reuse the same value for the earlier buf_offset computation."
        }
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      "metrics": [
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          "cvssV3_1": {
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
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              "value": "AV:L - The bug is reached only through binder IPC via ioctl(BINDER_WRITE_READ) on /dev/binder or binderfs with BC_TRANSACTION/BC_TRANSACTION_SG, requiring local access to the binder device; there is no network, Bluetooth, or physical bus path to binder_transaction().\nAC:L - This is a deterministic logic error, not a race: on every transaction to a txn_security_ctx node, security_release_secctx() zeroes lsmctx.len before sg_buf_end_offset is computed, so the attacker reliably gains extra scatter-gather space by crafting BINDER_TYPE_PTR objects.\nPR:L - binder_open() has no capability check; on Android any untrusted_app can open /dev/binder and send transactions, and on other systems binderfs is mountable from user namespaces, so only basic local user access is required\u2014not real root.\nUI:N - Exploitation is driven entirely by the attacker\u0027s own binder client sending a crafted transaction; no victim user action such as opening a file, mounting a filesystem, or approving a prompt is required.\nS:U - Impact is overwriting kernel-managed LSM security context data within a binder transaction buffer to spoof caller identity for privilege escalation; this is standard local kernel/Android sandbox bypass, not a VM, hypervisor, or IOMMU boundary crossing.\nC:H - The inflated sg_buf_end_offset permits scatter-gather copies to overwrite the kernel-written secctx region\u2014an out-of-bounds write relative to the intended SG boundary that can forge sender SELinux labels seen by privileged receivers, enabling unauthorized data access.\nI:H - Attacker-controlled user data from BINDER_TYPE_PTR copies overwrite the kernel-placed LSM security context string in the transaction buffer, directly corrupting integrity of trusted caller-identity metadata used for authorization decisions by privileged binder services.\nA:H - Kernel transaction-buffer corruption delivered to privileged Android framework/system services can crash critical binder receivers or destabilize the device; per kernel CVSS guidance, out-of-bounds writes and memory corruption in kernel IPC paths warrant High availability impact."
            }
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        "dateUpdated": "2026-08-17T05:39:07.025Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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        },
        {
          "url": "https://git.kernel.org/stable/c/b34826e55aad3520ec813f1f367c11b24b29dc9f"
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    "cveId": "CVE-2026-68458",
    "datePublished": "2026-08-15T05:51:18.975Z",
    "dateReserved": "2026-07-30T09:28:09.395Z",
    "dateUpdated": "2026-08-17T05:39:07.025Z",
    "state": "PUBLISHED"
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      "percentile": "0.0261"
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-17T14:55:06+00:00",
      "cve": "CVE-2026-68458",
      "id": "CVE-2026-68458",
      "initial_release_date": "2026-08-15T00:00:00+00:00",
      "product_status:known_not_affected": "274",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: binder: cache secctx size before release zeroes it",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-68458.json",
      "version": "3"
    }
  }
}



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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
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