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CVE-2026-87886

From Exploited flaws, HARD’s guide to the flaws being used in attacks · Checked
This article is about a flaw in Acronis Backup. For every flaw being used in attacks, see Exploited flaws.

CVE-2026-87886 is a security flaw in Acronis Backup. Someone who already has a foothold can use Acronis Backup to take full control of the machine. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 16 Sep 2026.[1]

Acronis Backup is business software or equipment. Most families won’t have it, but attackers break into it to get inside companies, and from there to what those companies hold about their customers, patients and staff. Fixed in version 1.9.3.1021, 1.8.11.638 and 1.2.3.238.

Description

CISA calls it an incorrect default permissions in Acronis Backup. In its words: “Acronis Backup plugin for cPanel & WHM and extension for Plesk contains an incorrect default permissions vulnerability that could allow for privilege escalation.”[1]

The CVE record adds: “Local privilege escalation due to insecure file permissions. The following products are affected: Acronis Backup plugin for cPanel & WHM (Linux) before build 1.9.3.1021, Acronis Backup extension for Plesk (Linux) before build 1.8.11.638, Acronis Backup plugin for DirectAdmin (Linux) before build 1.2.3.238.”[2]

The underlying weakness is CWE-276, in MITRE’s list of common software weaknesses.

It scores 7.8 out of 10 on the Common Vulnerability Scoring System, which rates it high, scored by the organisation that published the CVE using CVSS 3.0.[2]

Affected versions

NVD’s record lists these fixed versions: in each line, everything before the version shown is affected.[2]

ProductFixed in
Acronis Backup plugin for cPanel & WHM1.9.3.1021
Acronis Backup extension for Plesk1.8.11.638
Acronis Backup plugin for DirectAdmin1.2.3.238

Most families won’t have Acronis Backup; it’s for whoever looks after IT at work.

Exploitation

CISA added it to its catalog of known exploited vulnerabilities on 16 Sep 2026. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 19 Sep 2026 to fix it.[1]

FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at under 1%. That’s in the top 86% of the flaws it scores.[4]

CISA assesses it as not automatable: each attack takes some work.

CISA doesn’t say who was attacked, or how.

Fix

Acronis has published a fix or advice.[3] CISA’s required action: “Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes).”[1]

  1. Check whether you use it.Acronis Backup is business software or equipment, so most families won’t have it. If you run a business, or work from home on company equipment, ask whoever looks after your IT.
  2. Send this page to your IT person.Ask them to confirm it’s fixed (fixed in version 1.9.3.1021, 1.8.11.638 and 1.2.3.238), or not in use. CISA gave US government agencies until 19 Sep 2026 to fix it.
  3. If it can’t be fixed, take it offline.CISA’s advice when there’s no fix is to stop using the product, or take it off the internet, until there is one.

You can’t fix someone else’s server, but you can watch for what follows a break-in like this: a breach notice, a password reset you didn’t ask for, or a scam message that knows things it shouldn’t. HARD watches for those for you and your family.

Timeline

DateEvent
CISA adds it to its catalog of flaws known to be used in attacks.[1]
The flaw is made public in the National Vulnerability Database, with a severity score of 7.8.[2]
CISA’s deadline for US government agencies to fix it.[1]
FIRST puts the odds of it being used in attacks in the next 30 days at under 1%.[4]

See also

Other Acronis flaws

  • CVE-2023-45249, Acronis Cyber Infrastructure (ACI): insecure default password ·

Similar flaws

  • CVE-2024-55956, Cleo products: unauthenticated file upload ·
  • CVE-2024-51378, CyberPersons CyberPanel: incorrect default permissions ·
  • CVE-2024-51567, CyberPersons CyberPanel: incorrect default permissions ·
  • CVE-2022-22948, VMware vCenter Server: incorrect default file permissions ·

Added the same day

  • CVE-2026-76460, Cisco Identity Services Engine: incorrect use of privileged APIs ·
  • CVE-2026-58704, Google Pixel: improper authorization ·

References

  1. ^ Cybersecurity and Infrastructure Security Agency. “Acronis Backup Incorrect Default Permissions Vulnerability”. Known Exploited Vulnerabilities Catalog, added 16 Sep 2026.
  2. ^ National Institute of Standards and Technology. “CVE-2026-87886 Detail”. National Vulnerability Database, published 17 Sep 2026.
  3. ^ Acronis. Advisories and fixes: security-advisory.acronis.com.
  4. ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.002, percentile 14.2, 31 Oct 2026.
  5. CVE Program. “CVE-2026-87886”. The official CVE record.

This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.