CVE-2026-83742
Received
Received - Intake
Unsigned Integer Underflow in wolfSSH Path Handling
Vulnerability report for CVE-2026-83742, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-10-07
Last updated on: 2026-10-07
Assigner: wolfSSL Inc.
Description
Description
Unsigned integer underflow in wstrncat() in src/port.c in wolfSSL wolfSSH from v1.4.11 through v1.5.0 on non-Windows platforms allows an authenticated remote attacker to write one out-of-bounds null byte past the end of a stack buffer by sending a crafted SFTP path. wolfSSH_RealPath() in src/ssh.c appends each path component with a remaining-size bound (outSz - curSz) rather than the full destination size, so once the accumulated path reaches half the output buffer the size_t computation n - strlen(s1) - 1 wraps to near SIZE_MAX. The strncat() call is then effectively unbounded and copies the whole component; when that component exactly fills the remainder of the buffer, its terminating null is written one byte past the end. The caller's own length check keeps the copied data inside the buffer, so the overflow is limited to that single null byte, which may corrupt an adjacent stack value and crash the process. Applications that call the public wolfSSH_RealPath() with an output buffer smaller than the input path are additionally exposed to an unbounded copy, because the word32 expression outSz - segSz in that length check also wraps.
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| wolfSSL | Inc. | wolfSSH 1.4.11 |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-193 | A product calculates or uses an incorrect maximum or minimum value that is 1 more, or 1 less, than the correct value. |
| CWE-191 | The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result. |
| CWE-121 | A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function). |
