# CVE-2026-17591: Libarchive: libarchive: use-after-free via aliased mac metadata copy

CVE-2026-17591 is fixed in libarchive on 1 platform by DEBIAN-CVE-2026-17591 (version 3.8.9-1), released October 17, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-17591
- Priority: Routine
- CVSS: 3.6 (Low)
- EPSS: 0.0015
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Oct 16, 2026
- Weakness: Use After Free
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-17591

## Description

A flaw was found in libarchive. An attacker can cause a Denial of Service (DoS) or potential information disclosure due to a use-after-free vulnerability, which occurs when a program reads memory that has already been released. This issue arises when the archive_entry_copy_mac_metadata() function deallocates an internal buffer before completing a data copy. An attacker who can supply input to an application utilizing this function can trigger the flaw to crash the application or read uninitialized memory data.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | libarchive Debian 14 | 3.8.9-1 | [DEBIAN-CVE-2026-17591](https://patchblox.com/security/data/fix/linux/debian-cve-2026-17591.md) | Oct 17, 2026 |

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Data as of 2026-11-08T13:06:02Z 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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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