Description
libsmb2 through 6.2 contains an integer underflow vulnerability in decode_acl that allows malicious SMB servers to trigger heap out-of-bounds reads via crafted security descriptors. Attackers controlling a server or intercepting unsigned sessions can send an AclSize below 8 in a QUERY_INFO reply, bypassing ACE bounds checks and crashing the client.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| sahlberg | libsmb2 | ≤ 6.2 | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | libsmb2 | No fix yet | — |
| Debian 13 | libsmb2 | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | libsmb2 | No fix yet | — |
| Ubuntu 26.04 LTS | libsmb2 | No fix yet | — |
References
- https://hackmd.io/@haind-pwn/libsmb2-query-info-reply-oob-read technical-description exploit
- https://github.com/sahlberg/libsmb2/blob/d67e213a5c4e7e4969fd81f0b95e4ca5831fbba1/lib/smb2-data-security-descriptor.c#L266 technical-description
- https://github.com/sahlberg/libsmb2/commit/523abe20be3207011a936db47f1d3bab79c05450 patch
- https://github.com/sahlberg/libsmb2 product
- VulnCheck Advisory: libsmb2 through 6.2 Heap Out-of-Bounds Read via decode_acl Integer Underflow third-party-advisory