High severity · published Apr 24, 2026
CVE-2026-31613
smb: client: fix OOB reads parsing symlink error response
8.1
CVSS
0.4%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
High
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 33% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
KE
Kernel · Linux
6.1 before 6.18.24; 6.19 before 6.19.14; 7.0 before 7.0.1 · source: NVD
LI
Linux · Linux
76894f3e2f71177747b8b4763fb180e800279585 before 043834e72337ee7b4e9685859888623ba1504ac7; 76894f3e2f71177747b8b4763fb180e800279585 before d65a64755a3df68a2fd19d2a81395e9f723aca23; 76894f3e2f71177747b8b4763fb180e800279585 before 20ac98f0eb6047edb73c9a27af782bdde08b3757; 76894f3e2f71177747b8b4763fb180e800279585 before e0dd90d14cbbf318157ea8e3fb62ee68a28655ed; 76894f3e2f71177747b8b4763fb180e800279585 before 781902e069f4ecb6c3b83502f181972c1446110a; 76894f3e2f71177747b8b4763fb180e800279585 before a66ef2e7ed837325c5600f8617d5ee0a0a149fdd; +4 more · source: vendor
SS
SIMATIC S7-1500 TM MFP - GNU/Linux subsystem · Siemens
0 · source: CISA
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-31613
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-31613
git.kernel.org
https://git.kernel.org/stable/c/043834e72337ee7b4e9685859888623ba1504ac7
git.kernel.org
https://git.kernel.org/stable/c/20ac98f0eb6047edb73c9a27af782bdde08b3757
Patch
https://git.kernel.org/stable/c/3df690bba28edec865cf7190be10708ad0ddd67e
Patch
https://git.kernel.org/stable/c/781902e069f4ecb6c3b83502f181972c1446110a
Patch
https://git.kernel.org/stable/c/a66ef2e7ed837325c5600f8617d5ee0a0a149fdd
git.kernel.org
https://git.kernel.org/stable/c/d65a64755a3df68a2fd19d2a81395e9f723aca23
More from Kernel
9.8
CVE-2025-39682
tls: fix handling of zero-length records on the rx_list
8.8
CVE-2026-53266
netfilter: bridge: make ebt_snat ARP rewrite writable
8.8
CVE-2013-6282
Linux Kernel Improper Input Validation Vulnerability
8.4
CVE-2022-0185
Linux Kernel Heap-Based Buffer Overflow Vulnerability
8.4
CVE-2013-2094
Linux Kernel Privilege Escalation Vulnerability
