CVE-2026-31613 (GCVE-0-2026-31613)

Vulnerability from cvelistv5 – Published: 2026-04-24 14:42 – Updated: 2026-10-19 18:56
VLAI
Title
smb: client: fix OOB reads parsing symlink error response
Summary
In the Linux kernel, the following vulnerability has been resolved: smb: client: fix OOB reads parsing symlink error response When a CREATE returns STATUS_STOPPED_ON_SYMLINK, smb2_check_message() returns success without any length validation, leaving the symlink parsers as the only defense against an untrusted server. symlink_data() walks SMB 3.1.1 error contexts with the loop test "p < end", but reads p->ErrorId at offset 4 and p->ErrorDataLength at offset 0. When the server-controlled ErrorDataLength advances p to within 1-7 bytes of end, the next iteration will read past it. When the matching context is found, sym->SymLinkErrorTag is read at offset 4 from p->ErrorContextData with no check that the symlink header itself fits. smb2_parse_symlink_response() then bounds-checks the substitute name using SMB2_SYMLINK_STRUCT_SIZE as the offset of PathBuffer from iov_base. That value is computed as sizeof(smb2_err_rsp) + sizeof(smb2_symlink_err_rsp), which is correct only when ErrorContextCount == 0. With at least one error context the symlink data sits 8 bytes deeper, and each skipped non-matching context shifts it further by 8 + ALIGN(ErrorDataLength, 8). The check is too short, allowing the substitute name read to run past iov_len. The out-of-bound heap bytes are UTF-16-decoded into the symlink target and returned to userspace via readlink(2). Fix this all up by making the loops test require the full context header to fit, rejecting sym if its header runs past end, and bound the substitute name against the actual position of sym->PathBuffer rather than a fixed offset. Because sub_offs and sub_len are 16bits, the pointer math will not overflow here with the new greater-than.
Severity
8.1 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-16 15:11 UTC
CWE
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 7033 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 76894f3e2f71177747b8b4763fb180e800279585 , < 043834e72337ee7b4e9685859888623ba1504ac7 (git)
Affected: 76894f3e2f71177747b8b4763fb180e800279585 , < d65a64755a3df68a2fd19d2a81395e9f723aca23 (git)
Affected: 76894f3e2f71177747b8b4763fb180e800279585 , < 20ac98f0eb6047edb73c9a27af782bdde08b3757 (git)
Affected: 76894f3e2f71177747b8b4763fb180e800279585 , < e0dd90d14cbbf318157ea8e3fb62ee68a28655ed (git)
Affected: 76894f3e2f71177747b8b4763fb180e800279585 , < 781902e069f4ecb6c3b83502f181972c1446110a (git)
Affected: 76894f3e2f71177747b8b4763fb180e800279585 , < a66ef2e7ed837325c5600f8617d5ee0a0a149fdd (git)
Affected: 76894f3e2f71177747b8b4763fb180e800279585 , < 3df690bba28edec865cf7190be10708ad0ddd67e (git)
Affected: 2d046892a493d9760c35fdaefc3017f27f91b621 (git)
Affected: 6.0.16 , < 6.1 (semver)
guessed Create a notification for this product.
Linux Linux Affected: 6.1
Unaffected: 0 , < 6.1 (semver)
Unaffected: 6.1.175 , ≤ 6.1.* (semver)
Unaffected: 6.6.141 , ≤ 6.6.* (semver)
Unaffected: 6.12.91 , ≤ 6.12.* (semver)
Unaffected: 6.18.24 , ≤ 6.18.* (semver)
Unaffected: 6.19.14 , ≤ 6.19.* (semver)
Unaffected: 7.0.1 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem Affected: 0 , < * (custom)
guessed Create a notification for this product.
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      "product_status:known_affected": "22",
      "product_status:known_not_affected": "42",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: smb: client: fix OOB reads parsing symlink error response",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-31613.json",
      "version": "3"
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              "programFiles": [
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}



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