CVE-2026-87886: Acronis Backup Incorrect Default Permissions Vulnerability

Recommended actionProtect now

CISA confirms exploitation in the wild and lists 2026-09-19 as the remediation due date.

Fix not verified

What, why and how

Acronis Backup plugin for cPanel & WHM and extension for Plesk contains an incorrect default permissions vulnerability that could allow for privilege escalation.

What

Acronis Backup plugin for cPanel & WHM and extension for Plesk contains an incorrect default permissions vulnerability that could allow for privilege escalation.

Why

During installation, installed file permissions are set to allow anyone to modify those files.

How

An attacker operating through local access may attempt exploitation with low privileges. If successful, the issue may gain additional privileges.

What

Acronis Backup plugin for cPanel & WHM and extension for Plesk contains an incorrect default permissions vulnerability that could allow for privilege escalation.

Why

During installation, installed file permissions are set to allow anyone to modify those files.

How

An attacker operating through local access may attempt exploitation with low privileges. If successful, the issue may gain additional privileges.

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation

Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.

Confirmed in the wild

CISA added this CVE to its Known Exploited Vulnerabilities catalogue on 2026-09-16.

Public PoC / exploit material

Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.

None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path: local access → Incorrect Default Permissions → gain additional privileges
Attack surface: Local
Privileges required: Low: a basic authenticated account is required
User interaction: None
Attack complexity: Low: no specialised conditions are recorded
Security boundary: Unchanged: impact remains within the vulnerable component's security authority
Weakness ? CWE means Common Weakness Enumeration: a standard category for the underlying weakness.: CWE-276 ↗
CWE-276: Incorrect Default Permissions. During installation, installed file permissions are set to allow anyone to modify those files.
CVSS vector ? CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Common Vulnerability Scoring System 3.0: the compact vector below is decoded into plain language.
AVLocalAttack vector: The attacker needs local access to the vulnerable system.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRLowPrivileges required: The attacker needs basic user-level privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CHighConfidentiality impact: A successful attack can cause a major loss.IHighIntegrity impact: A successful attack can cause a major loss.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land: The issue can support a local privilege or sandbox boundary transition; normal system utilities may then be available in the gained context.

Privilege escalationCWE-276CISA KEV

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

ENISA EUVD · EUVD-2026-82595Known-exploited evidence recorded

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.

Official EUVD record ↗

Cyber Security Agency of Singapore · English · CSA-SB-20260923Security Bulletin 23 Sep 2026

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 23 Sep 2026, published on 23 September 2026. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗

NBSZ-NKI · Hungarian · cve-2026-87886CVE-2026-87886

A telepítés során a telepített fájlok jogosultságai úgy vannak beállítva, hogy azokat bárki módosíthatja.

Official advisory ↗

CSIRT Italia · Italian · acronis-rilevato-sfruttamento-in-rete-della-cve-2026-87886Acronis: rilevato sfruttamento in rete della CVE-2026-87886

La vulnerabilità identificata tramite la CVE-2026-87886 , di tipo " Local Privilege Escalation ", e con CVSS 3.0 pari a 7.8, interessa i plugin di backup Acronis per Plesk, cPanel e WHM, ed è dovuta a una configurazione non sicura dei permessi dei file, che consente a un utente locale con privilegi limitati di manipolare file o percorsi utilizzati dal servizio di backup, che viene eseguito con privilegi elevati. Un attaccante che disponga di accesso locale al sistema potrebbe sfruttare tale vulnerabilità per eseguire codice arbitrario con privilegi root, compromettendo l'integrità e la riservatezza dell'host interessato.

Official advisory ↗

KISA KrCERT/CC · Korean · KNVD-6958美 CISA 발표 주요 Exploit 정보공유(Update. 2026-09-16)

Acronis Backup Incorrect Default Permissions Vulnerability

Official advisory ↗

Patch and workaround

Operational remediation based on structured source evidence.

Status ? Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.: Fix not verified
Affected: Acronis Backup plugin for cPanel & WHM: unspecified < 1.9.3.1021
Acronis Backup extension for Plesk: unspecified < 1.8.11.638
Acronis Backup plugin for DirectAdmin: unspecified < 1.2.3.238
Fixed: No fixed version is explicitly recorded in the structured CVE data.
Action: No verified patch reference is present in the current structured sources. Check the vendor advisory before making a change.
Workaround: No verified workaround is recorded. Limit untrusted access and use least privilege until authoritative guidance is available.

Evidence and provenance

Published 17 Sept 2026 · Last source change 18 Sept 2026, 14:33 UTC · CWE-276 · Incorrect Default Permissions

CVE recordCVE.org · 5.2

CVSS sourceCNA

EPSS source

The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.

FIRST · tracked since 2026-09-18

European sourceENISA EUVD · EUVD-2026-82595

Product sourceCISA KEV

Remediation sourceCVE/CNA references

CWE sourceCNA

NVD statusNVD enriched

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗

18 Sep 2026, 14:33 UTC
Public exploit evidencePublic exploit evidence changed from Public exploit reference to No public exploit.
Before
Public exploit reference
After
No public exploit
CVE.org ↗
18 Sep 2026, 14:33 UTC
Public exploit evidencePublic exploit evidence changed from No public exploit to Public exploit reference.
Before
No public exploit
After
Public exploit reference
cisa.gov ↗
18 Sep 2026, 12:28 UTC
Vendor guidanceAuthoritative vendor guidance changed: added vendor advisory: security-advisory.acronis.com/SEC-10986.
Before
no authoritative guidance recorded
After
vendor advisory: security-advisory.acronis.com/SEC-10986
security@acronis.com ↗
18 Sep 2026, 12:28 UTC
Public exploit evidencePublic exploit evidence changed from Public exploit reference to No public exploit.
Before
Public exploit reference
After
No public exploit
CVE.org ↗
18 Sep 2026, 12:28 UTC
Public exploit evidencePublic exploit evidence changed from No public exploit to Public exploit reference.
Before
No public exploit
After
Public exploit reference
cisa.gov ↗
18 Sep 2026, 00:06 UTC
ENISA known-exploited stateENISA EUVD now records this CVE in its known-exploited dataset.
Before
not listed in ENISA EUVD known-exploited dataset
After
listed in ENISA EUVD known-exploited dataset (EUVD-2026-82595)
ENISA EUVD ↗
18 Sep 2026, 00:06 UTC
ENISA EUVD mappingEUVD-2026-82595 was added to the official ENISA EUVD mapping for this CVE.
Before
not recorded
After
{"euvdId":"EUVD-2026-82595"}
ENISA EUVD ↗
17 Sep 2026, 22:57 UTC
Affected versionsThe structured affected or fixed version information changed.
Before
No structured affected-product or version range is currently available from the CVE record or NVD. · Fixed: No fixed version is explicitly recorded in the structured CVE data.
After
Acronis Backup plugin for cPanel & WHM: unspecified < 1.9.3.1021; Acronis Backup extension for Plesk: unspecified < 1.8.11.638; Acronis Backup plugin for DirectAdmin: unspecified < 1.2.3.238 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
CISA KEV ↗
17 Sep 2026, 22:57 UTC
SeveritySeverity changed from Unknown to High.
Before
Unknown
After
High
CNA ↗
17 Sep 2026, 22:57 UTC
CVSS scoreCVSS score changed from not recorded to 7.8 (CVSS 3.0 · CNA · CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H).
Before
not recorded
After
7.8 (CVSS 3.0 · CNA · CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)
CNA ↗
17 Sep 2026, 14:07 UTC
BlackTree coverageBlackTree article coverage changed from no BlackTree article to 1 BlackTree article.
Before
no BlackTree article
After
1 BlackTree article
BlackTree editorial ↗
16 Sep 2026, 18:47 UTC
Catalogue recordCVE added to the BlackTree catalogue.
CISA KEV ↗

2026-09-17CVE published

2026-09-16Added to CISA KEV

ENISA EUVD · EUVD-2026-82595↗CISA KEV record↗CVE authority or vendor reference↗Official CVE record (CNA and ADP data)↗NVD record↗

Technical terms and abbreviations used in this report

CVE: Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS: Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS: Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE: Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA: CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP: Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD: National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT: A computer security incident response team that publishes warnings or coordinates incident response.
PoC: Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF: Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL: Living off the land: abuse of legitimate tools or system functions during an attack.

Acronis Backup Incorrect Default Permissions Vulnerability

Published severity in operational context

Evidence used

Compensating controls

Verification

National CERT insights
?
CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

ENISA European Vulnerability Database

EUVD-2026-82595

What, why and how

Exploit reality and attack path

Official authority intelligence

Patch and workaround

Evidence and provenance

What changed after publication