Answer in brief
CVE-2026-89638 records a High severity (CVSS 7.8) vulnerability in smb: client: clear setuid/setgid bit on write with cifsacl/modefromsid/posix extensions. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic), Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 7.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Linux/Linux (generic), Linux/Linux (generic), Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=d32c4f2626acc385d5187bd5c0c24f442328dc60 <b10015807e4c628095d1d1d1c9307efc8cdd9e1b || >=d32c4f2626acc385d5187bd5c0c24f442328dc60 <69bfe810ecd1e0387d8975d711cd326341d13c6e || >=d32c4f2626acc385d5187bd5c0c24f442328dc60 <b8e5dc4f95e5484159b343903f302eb6d783f2e6 | b10015807e4c628095d1d1d1c9307efc8cdd9e1b, 69bfe810ecd1e0387d8975d711cd326341d13c6e, b8e5dc4f95e5484159b343903f302eb6d783f2e6 |
| Linux/Linuxgeneric | 2.6.24 | Not reported |
| Linux/Linuxgeneric | >=d32c4f2626acc385d5187bd5c0c24f442328dc60 <58b23fc9fb580432470d6c5da3c1e5660dba9fbc || >=d32c4f2626acc385d5187bd5c0c24f442328dc60 <b10015807e4c628095d1d1d1c9307efc8cdd9e1b || >=d32c4f2626acc385d5187bd5c0c24f442328dc60 <69bfe810ecd1e0387d8975d711cd326341d13c6e || >=d32c4f2626acc385d5187bd5c0c24f442328dc60 <b8e5dc4f95e5484159b343903f302eb6d783f2e6 | 58b23fc9fb580432470d6c5da3c1e5660dba9fbc, b10015807e4c628095d1d1d1c9307efc8cdd9e1b, 69bfe810ecd1e0387d8975d711cd326341d13c6e, b8e5dc4f95e5484159b343903f302eb6d783f2e6 |
| Linux/Linuxgeneric | >=d32c4f2626acc385d5187bd5c0c24f442328dc60 <7ceb6f7cb8f8f2b094e0dcdaf75757775d231378 || >=d32c4f2626acc385d5187bd5c0c24f442328dc60 <58b23fc9fb580432470d6c5da3c1e5660dba9fbc || >=d32c4f2626acc385d5187bd5c0c24f442328dc60 <b10015807e4c628095d1d1d1c9307efc8cdd9e1b || >=d32c4f2626acc385d5187bd5c0c24f442328dc60 <69bfe810ecd1e0387d8975d711cd326341d13c6e || >=d32c4f2626acc385d5187bd5c0c24f442328dc60 <b8e5dc4f95e5484159b343903f302eb6d783f2e6 | 7ceb6f7cb8f8f2b094e0dcdaf75757775d231378, 58b23fc9fb580432470d6c5da3c1e5660dba9fbc, b10015807e4c628095d1d1d1c9307efc8cdd9e1b, 69bfe810ecd1e0387d8975d711cd326341d13c6e, b8e5dc4f95e5484159b343903f302eb6d783f2e6 |
Published upstream
Sep 11, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Oct 21, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Sep 11, 2026
In the Linux kernel, the following vulnerability has been resolved: smb: client: clear setuid/setgid bit on write with cifsacl/modefromsid/posix extensions When a file has the setuid or setgid bit set and is written to, the VFS strips those bits and issues a setattr with ATTR_KILL_SUID/ATTR_KILL_SGID together with an ATTR_MODE carrying the already-cleared mode. Both cifs_setattr_unix() and cifs_setattr_nounix() unconditionally dropped ATTR_MODE in that case: /* skip mode change if it's just for clearing setuid/setgid */ if (attrs->ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) attrs->ia_valid &= ~ATTR_MODE; This is fine for the default mount, where the mode is only emulated via the DOS read-only attribute and cannot represent the setuid/setgid bits anyway. However, with the "cifsacl" or "modefromsid" mount options the mode is stored on the server through an ACL (id_mode_to_cifs_acl()), with the SMB3.1.1 POSIX extensions the mode is sent to the server directly, and with the SMB1 Unix extensions (cifs_setattr_unix) the mode is sent via CIFSSMBUnixSetPathInfo(). In all those cases dropping ATTR_MODE means the cleared mode is never pushed to the server, so the setuid/setgid bit survives the write. This is a security issue: on local filesystems the setuid bit is stripped when a file is written, but over these cifs.ko mounts the bit persists on the server, potentially allowing an unexpected privilege escalation on subsequent execution. Fix this in two places: 1. cifs_setattr_nounix(): only take the "skip mode change" shortcut when the mode is emulated via the DOS read-only attribute (i.e. neither cifsacl/modefromsid nor the SMB3.1.1 POSIX extensions are in effect), so that the cleared mode is propagated to the server in the ACL / POSIX cases. 2. cifs_setattr_unix(): this function is only called when Unix extensions are in effect, so the mode is always stored on the server. Remove the shortcut entirely so that the cleared mode is always pushed.
Quoted source text, attributed separately from HOL analysis.