ksmbd: validate num_subauth when copying ACE in set_ntacl_dacl
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- Fix
- Fixed in 6.1.184, 6.6.148, 6.12.101, 6.18.42, 7.1.6
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
- Exploitation: none
- Automatable: no
- Technical impact: partial
Summary
In the Linux kernel, the following vulnerability has been resolved: ksmbd: validate num_subauth when copying ACE in set_ntacl_dacl set_ntacl_dacl() copies each ACE from the attacker-controlled stored security descriptor verbatim into the response DACL without checking sid.num_subauth. The ACE bytes (including an unchecked num_subauth) originate from an authenticated SMB2_SET_INFO(SecInfo=DACL) that is stored raw via ksmbd_vfs_set_sd_xattr(); parse_dacl() rejects a bad ACE with `break` rather than an error, so parse_sec_desc() still returns success and the malformed SD reaches the xattr intact. On a subsequent SMB2_QUERY_INFO(SecInfo=DACL) for an inode carrying a POSIX access ACL, build_sec_desc() -> set_ntacl_dacl() -> set_posix_acl_entries_dacl() walks the copied ACEs and reads ntace->sid.sub_auth[ntace->sid.num_subauth - 1] with num_subauth taken straight from the stored SD. Since sub_auth[] is fixed at SID_MAX_SUB_AUTHORITIES (15), a crafted num_subauth (e.g. 255) drives an out-of-bounds heap read of ~1 KB with an offset fully controlled by an authenticated client. The sibling functions already gate this field: parse_dacl() -- num_subauth == 0 || > SID_MAX_SUB_AUTHORITIES parse_sid() -- num_subauth > SID_MAX_SUB_AUTHORITIES smb_copy_sid() -- min_t(u8, num_subauth, SID_MAX_SUB_AUTHORITIES) set_ntacl_dacl() is the lone inconsistent path that omits the check. Add the same num_subauth validation in set_ntacl_dacl() before copying the ACE, matching the gate already enforced by parse_dacl().
Timeline
- CVE published
- CISA SSVC assessment
Exploitation: none · Automatable: no · Technical impact: partial
- Record last updated
Affected versions
- Linux Linux
From e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 · fixed in 26cb845e22a00c85bf566337417fa33492395f10; From e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 · fixed in e31fada5143784bc05c7ae44c79eed9b7a2e147e; From e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 · fixed in fb3dc8e6da46a1ccad1956cda57de29d9b3033e0; From e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 · fixed in b6d3cc6a524416dfdb2b47e4bba2e7e20011d056; From e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 · fixed in 5acbd3012fd4a7ccfebd91ea6f784120084eb897; From e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 · fixed in 47f0b34f6bc98ed85bfdc293e8f3e432ec24958d
- Linux Linux
5.15
- KernelLinux
From 5.15.0 · fixed in 6.1.184; From 6.2.0 · fixed in 6.6.148; From 6.7.0 · fixed in 6.12.101; From 6.13.0 · fixed in 6.18.42; From 6.19.0 · fixed in 7.1.6