CVE-2026-83742
Wolfssh: stack buffer overflow can lead to denial of service
- Risk score
- 59/100
- CVSS
- 8.8 v3.1
- Exploit chance (30 days)
- 0.4%
- Published
- 7 Oct 2026
Open in the live forecast Today's forecast
What to know
- What it is
- 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 co…
- Affected
- Wolfssh
- Fix
- Apply the vendor's security update; see the linked advisory.
- Exploitation
- No known exploitation
Story map
At a glance
Wolfssh: Amber, patch this week. In wolfSSH through 1.5.0 built with --enable-fwd, DoChannelOpen() in src/internal.c gates only direct-tcpip channel opens with the forwarding policy callback. forwarded-tcpip opens are admitted without an authorization check and are not capped in number, allowing a malicious SSH peer to make an endpoint allocate unbou…
The flaws
- CVE-2026-83742: Stack buffer overflow can lead to denial of service (CVSS 8.8 · EPSS 0%)
- CVE-2026-81535: Missing authorisation (CVSS 9.1 · EPSS 0%)
- CVE-2026-83540: Authentication bypass (CVSS 8.8 · EPSS 0%)
- CVE-2026-16516: WolfSSH does not validate that the ECDSA curve identifier in a KEXDH_REPLY host key blob matches… (CVSS 7.4 · EPSS 0%)
The fix
Fix: Apply the vendor's security update; see the linked advisory.
Who is exposed: Wolfssh
Where it stands
- No known exploitation
Connects to
- Same weakness: Stack buffer overflow (CWE-121). 197 other warnings in 30 days
- Same product: Earlier Wolfssh warnings. 1 in the last 90 days
Why it is Yellow
- CVSS 8.8 high
References
Original 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.
Last activity 7 Oct 2026. Patch Forecast updates every hour.