hashcat contains a heap-based buffer overflow (out-of-bounds write) in the outfile_write() function in src/outfile.c. When assembling output into a fixed-size buffer (HCBUFSIZ_LARGE, ~16 MB), the function sequentially appends the username, separator, hash, and plaintext via memcpy without validating that the accumulated length stays within the buffer capacity. When run with --username --show against a crafted hash file containing an oversized username that nearly fills the buffer, the total assembled output exceeds the buffer, causing a heap buffer overflow that can corrupt memory and crash the process.
Attack Parameters
Attack Vector
Local
Requires local access
Attack Complexity
Low
Easy to exploit
Attack Requirements
None
No additional conditions
Privileges Required
None
No privileges needed
User Interaction
Passive
Minimal interaction
Impact Assessment
Confidentiality
None
No data leak
Integrity
Low
Partial data modification
Availability
High
Complete denial of service
CVSS Vector v4.0
Weakness Type (CWE)
References 5
https://github.com/hashcat/hashcat
disclosure@vulncheck.com
https://github.com/hashcat/hashcat/blob/v7.1.2/src/outfile.c#L654-L668
disclosure@vulncheck.com
https://github.com/hashcat/hashcat/commit/68f56a2d8712867a8520bf4dcf07f6145c23d…
disclosure@vulncheck.com
https://github.com/hashcat/hashcat/issues/4740
disclosure@vulncheck.com
https://www.vulncheck.com/advisories/hashcat-through-heap-buffer-overflow-in-ou…
disclosure@vulncheck.com