wstrncat() unsigned integer underflow leads to an off-by-one null write in wolfSSH on non-Windows platforms
Summary
| CVE | CVE-2026-83742 |
|---|---|
| State | PUBLISHED |
| Assigner | wolfSSL |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-10-07 03:16:59 UTC |
| Updated | 2026-10-13 14:29:47 UTC |
| 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. |
Risk And Classification
Primary CVSS: v4.0 5.3 MEDIUM from [email protected]
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:N/R:X/V:X/RE:X/U:X
EPSS: 0.003300000 probability, percentile 0.240550000 (date 2026-10-07)
Problem Types: CWE-121 | CWE-191 | CWE-193 | CWE-191 CWE-191 Integer Underflow (Wrap or Wraparound) | CWE-121 CWE-121 Stack-based Buffer Overflow | CWE-193 CWE-193 Off-by-one Error
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 4.0 | [email protected] | Secondary | 5.3 | MEDIUM | CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N/E:X/C... |
| 4.0 | CNA | CVSS | 5.3 | MEDIUM | CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N/AU:N |
| 3.1 | [email protected] | Primary | 8.8 | HIGH | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
CVSS v4.0 Breakdown
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:N/R:X/V:X/RE:X/U:X
CVSS v3.1 Breakdown
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD Known Affected Configurations (CPE 2.3)
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | WolfSSL Inc. | WolfSSH | affected 1.4.11 1.5.0 semver | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| github.com/wolfSSL/wolfssh/commit/822e4464560b467580ea37a2fc03b0988d88b71f | [email protected] | github.com | Patch |
| github.com/wolfSSL/wolfssh/commit/513e52b18927a4e3f7cf17ecaf107958e56139de | [email protected] | github.com | Patch |
| github.com/wolfSSL/wolfssh/pull/1084 | [email protected] | github.com | Patch |
| github.com/wolfSSL/wolfssh/commit/fbc7cd88a23b59a45a584020a4c7242d9bd70f35 | [email protected] | github.com | Patch |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Asif Nadaf <[email protected]>, Independent Security Researcher (en)