# CVE-2026-64139: linux: In the Linux kernel, the following vulnerability has been resolved:  ksmbd: fix SID memory leak in set_posix_acl_entr...

CVE-2026-64139 is fixed in linux on 1 platform, first by DEBIAN-CVE-2026-64139, released July 20, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-64139
- Priority: Routine
- CVSS: 5.5 (medium)
- EPSS: 0.0017
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jul 19, 2026

## Description

In the Linux kernel, the following vulnerability has been resolved:  ksmbd: fix SID memory leak in set_posix_acl_entries_dacl() on overflow  Commit 299f962c0b02 ("ksmbd: use check_add_overflow() to prevent u16 DACL size overflow") added check_add_overflow() guards that break out of the ACE-building loops in set_posix_acl_entries_dacl() when the accumulated DACL size would wrap past 65535.  However, each iteration allocates a struct smb_sid via kmalloc_obj() at the top of the loop and relies on the kfree(sid) call at the end of the loop body (the 'pass_same_sid' label in the first loop, and the explicit kfree at the tail of the second loop) to release it. The newly introduced 'break' statements bypass those kfree() calls, leaking the sid buffer every time an overflow is detected.  A malicious or malformed file with enough POSIX ACL entries to trip the overflow check will leak one or more struct smb_sid allocations on every request that touches the file's DACL, providing a trivial kernel memory exhaustion vector.  Free sid before breaking out of the loops to plug the leak.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 6.1.187-1 | [DEBIAN-CVE-2026-64139](https://patchblox.com/security/data/fix/linux/debian-cve-2026-64139.md) | Jul 20, 2026 |
| Linux | linux Debian 13.5 (trixie) | 6.12.94-1 | [DEBIAN-CVE-2026-64139](https://patchblox.com/security/data/fix/linux/debian-cve-2026-64139.md) | Jul 20, 2026 |
| Linux | linux Debian 14 | 7.0.12-1 | [DEBIAN-CVE-2026-64139](https://patchblox.com/security/data/fix/linux/debian-cve-2026-64139.md) | Jul 20, 2026 |

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Data as of 2026-11-09T01:18:40Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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