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Full vulnerability report · 2026
CVE-2026-88045High confidence

rclone: S3 multipart declared-length memory exhaustion

rclone · rclone

Official source article: GitHub GHSA-2P48-J3QC-RX9F ↗. Check the applicable product and release in the original source.

7.5HighCVSS 3.1
Recommended action
Within 7 days

High technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance.

Patch available
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityHighOperational priority:Critical, raised one band.upgradedsince 10 Sep 2026

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • A structured source references public exploit or proof-of-concept material.
  • The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
  • EPSS is 0.63% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict the affected network interface to trusted sources where business-safe.
  • Increase monitoring for the attack path and post-exploitation behaviour described in the report.

Verification

  1. Confirm that the asset runs rclone rclone and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: Within 3 daysRemediation target: Within 90 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Distribution package intelligence

Release-specific package status

Debian, ubuntu findings are scoped to the named distribution, release and source package. An absent finding does not mean a package is unaffected.

4 package states
Repository candidate not checked

A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.

Distribution releaseSource packageVendor stateFixed versionEvidence
Debian trixietrixie · sourcercloneNot affectedDebian marks this release not affected (fixed-version marker 0).Not published in this feedDebian Security Tracker ↗Source updated 5 Oct 2026
Debian bookwormbookworm · sourcercloneNot affectedDebian marks this release not affected (fixed-version marker 0).Not published in this feedDebian Security Tracker ↗Source updated 5 Oct 2026
Debian sidsid · sourcercloneNot affectedDebian marks this release not affected (fixed-version marker 0).Not published in this feedDebian Security Tracker ↗Source updated 5 Oct 2026
Ubuntu 24.04 LTSnoble · esm-appsrcloneUnder evaluationCanonical reports that the package might be affected and still needs evaluation or fixing.Not published in this feedCanonical Ubuntu Security ↗Source updated 5 Oct 2026
Open-source package ranges3 source-attributed ranges

These OSV and GitHub advisory ranges apply only to the named package and ecosystem. A listed fixed version is not a universal product patch or proof that an update is installed.

Ecosystem and packageAffected rangeFirst fixed versionEvidence
Gogithub.com/rclone/rcloneSEMVER: introduced 1.75.0; fixed 1.75.11.75.1OSV record ↗aggregator derived · 19 Sep 2026
Gogithub.com/rclone/rcloneSEMVER: introduced 1.75.0; fixed 1.75.11.75.1OSV record ↗aggregator derived · 19 Sep 2026
gogithub.com/rclone/rclone= 1.75.01.75.1GitHub advisory ↗upstream repository advisory · 10 Sep 2026
Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

1 current
CVE-2026-88045 · CSAF 2.0 · revision 3 · finalRed Hat Product Securitygithub.com/rclone/rclone: rclone: Memory exhaustion leading to Denial of Service
2 known not affected

The vendor explicitly states that these products are not affected by this CVE.

  • cryostat/cryostat-storage-rhel9 as a component of Cryostat 4
  • rhacm2/volsync-rhel9 as a component of Red Hat Advanced Cluster Management for Kubernetes 2
Summary
A flaw was found in rclone. A remote attacker can exploit a memory exhaustion vulnerability in the S3 streamed multipart path. By manipulating the `Content-Length` or `X-Amz-Decoded-Content-Length` headers, an attacker can cause the application to reserve excessive memory without sending the declared body. This can lead to the exhaustion of process or host memory, resulting in a Denial of Service (DoS).
Remediation
No remediation text is recorded.
Optional official sources

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

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2026-75588

No EUVD known-exploited evidence

rclone is a command-line program to sync files and directories to and from different cloud storage providers. From 1.75.0 until 1.75.1, the serve S3 streamed multipart path in cmd/serve/s3/multipart.go passes attacker-controlled contentLength to multipart.NewRW().Reserve before reading request-body bytes. waitForTurn admits the current part and one oversized part when the buffer is empty despite --multipart-streaming-buffer-limit, and lib/pool allocates 1 MiB pages according to Content-Length or X-Amz-Decoded-Content-Length. A network client can retain or multiply these reservations without sending the declared body, exhausting process or host memory or permanently blocking request handlers. Anonymous S3 deployments require no credentials, while deployments using auth_key require an accepted S3 key. This issue is fixed in version 1.75.1.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
7.5 · CVSS 3.1
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days

High technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance.

Patch available
01

What, why and how

rclone is a command-line program to sync files and directories to and from different cloud storage providers. From 1.75.0 until 1.75.1, the serve S3 streamed multipart path in cmd/serve/s3/multipart.go passes attacker-controlled contentLength to multipart.NewRW().Reserve before reading request-body bytes. waitForTurn admits the current part and one oversized part when the buffer is empty despite --multipart-streaming-buffer-limit, and lib/pool allocates 1 MiB pages according to Content-Length or X-Amz-Decoded-Content-Length. A network client can retain or multiply these reservations without sending the declared body, exhausting process or host memory or permanently blocking request handlers. Anonymous S3 deployments require no credentials, while deployments using auth_key require an accepted S3 key. This issue is fixed in version 1.75.1.

What

rclone is a command-line program to sync files and directories to and from different cloud storage providers. From 1.75.0 until 1.75.1, the serve S3 streamed multipart path in cmd/serve/s3/multipart.go passes attacker-controlled contentLength to multipart.NewRW().Reserve before reading request-body bytes. waitForTurn admits the current part and one oversized part when the buffer is empty despite --multipart-streaming-buffer-limit, and lib/pool allocates 1 MiB pages according to Content-Length or X-Amz-Decoded-Content-Length. A network client can retain or multiply these reservations without sending the declared body, exhausting process or host memory or permanently blocking request handlers. Anonymous S3 deployments require no credentials, while deployments using auth_key require an accepted S3 key. This issue is fixed in version 1.75.1.

Why

The product allocates memory based on an untrusted, large size value, but it does not ensure that the size is within expected limits, allowing arbitrary amounts of memory to be allocated.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

What

rclone is a command-line program to sync files and directories to and from different cloud storage providers. From 1.75.0 until 1.75.1, the serve S3 streamed multipart path in cmd/serve/s3/multipart.go passes attacker-controlled contentLength to multipart.NewRW().Reserve before reading request-body bytes. waitForTurn admits the current part and one oversized part when the buffer is empty despite --multipart-streaming-buffer-limit, and lib/pool allocates 1 MiB pages according to Content-Length or X-Amz-Decoded-Content-Length. A network client can retain or multiply these reservations without sending the declared body, exhausting process or host memory or permanently blocking request handlers. Anonymous S3 deployments require no credentials, while deployments using auth_key require an accepted S3 key. This issue is fixed in version 1.75.1.

Why

The product allocates memory based on an untrusted, large size value, but it does not ensure that the size is within expected limits, allowing arbitrary amounts of memory to be allocated.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

02

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.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
Reference recorded

CISA Vulnrichment records proof-of-concept exploitation in its SSVC data. BlackTree has not independently executed or validated exploit material.

Likely attack path
a network path → Memory Allocation with Excessive Size Value → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
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-789 ↗

CWE-789: Memory Allocation with Excessive Size Value. The product allocates memory based on an untrusted, large size value, but it does not ensure that the size is within expected limits, allowing arbitrary amounts of memory to be allocated.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CNoneConfidentiality impact: No direct loss is represented by this metric.INoneIntegrity impact: No direct loss is represented by this metric.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land
Stolen credentials, tokens and legitimate administration functions may provide continued access without deploying a large custom toolset.
NetworkUnauthenticatedCWE-789Public exploit reference
A

Official authority intelligence

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

ENISA EUVD · EUVD-2026-75588Official EUVD mapping

rclone is a command-line program to sync files and directories to and from different cloud storage providers. From 1.75.0 until 1.75.1, the serve S3 streamed multipart path in cmd/serve/s3/multipart.go passes attacker-controlled contentLength to multipart.NewRW().Reserve before reading request-body bytes. waitForTurn admits the current part and one oversized part when the buffer is empty despite --multipart-streaming-buffer-limit, and lib/pool allocates 1 MiB pages according to Content-Length or X-Amz-Decoded-Content-Length. A network client can retain or multiply these reservations without sending the declared body, exhausting process or host memory or permanently blocking request handlers. Anonymous S3 deployments require no credentials, while deployments using auth_key require an accepted S3 key. This issue is fixed in version 1.75.1.

Official EUVD record ↗
Cyber Security Agency of Singapore · English · CSA-SB-20260916Security Bulletin 16 Sep 2026

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 16 Sep 2026, published on 16 September 2026. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
CSIRT Italia · Italian · rclone-poc-pubblici-per-lo-sfruttamento-delle-cve-2026-88018-cve-2026-88044-cve-2026-88045-cve-2026-88016-e-cve-2026-88017Rclone: PoC pubblici per lo sfruttamento delle CVE-2026-88018, CVE-2026-88044, CVE-2026-88045, CVE-2026-88016 e CVE-2026-88017

Nel dettaglio le vulnerabilità per le quali risulta disponibile in rete un “proof of concept”: La vulnerabilità identificata tramite la CVE-2026-88018, di tipo "Authentication Bypass" e con CVSS 3.1 pari a 9.8, è dovuta a una gestione non corretta del processo di autenticazione SigV4 nel servizio S3 di rclone quando viene utilizzata la funzionalità--auth-proxy senza configurare il parametro--auth-key. Un attaccante remoto non autenticato potrebbe sfruttare tale vulnerabilità predisponendo richieste S3 opportunamente firmate con chiavi arbitrarie al fine di eludere completamente i controlli di autenticazione, ottenere accesso non autorizzato alle risorse esposte dal servizio e compromettere la riservatezza e l'integrità dei dati gestiti. La vulnerabilità identificata tramite la CVE-2026-88045, di tipo "Denial of Service" e con CVSS 3.1 pari a 7.5, è dovuta all'assenza di adeguati controlli sulla dimensione delle parti dichiarate durante le operazioni di upload multipart nel servizio S3 di rclone. Un attaccante remoto, autenticato oppure non autenticato nei casi in cui il servizio consenta l'accesso anonimo, potrebbe sfruttare tale vulnerabilità inviando richieste appositamente predisposte contenenti valori arbitrariamente elevati nei campi che specificano la dimensione dei dati da trasferire, inducendo il sistema ad allocare ingenti quantità di memoria prima della ricezione effettiva dei dati. Ciò potrebbe causare l'esaurimento delle risorse disponibili e la conseguente indisponibilità del servizio interessato. La vulnerabilità identificata tramite la CVE-2026-88016, di tipo "Security Restrictions Bypass " e con CVSS 3.1 pari a 7.1, è dovuta a un'applicazione non sicura delle operazioni di modifica dei metadati su file e directory in presenza di collegamenti simbolici. Un attaccante che abbia la possibilità di controllare il contenuto sincronizzato potrebbe sfruttare tale vulnerabilità predisponendo collegamenti simbolici malevoli al fine di applicare modifiche ai permessi, alla proprietà o ai timestamp di percorsi situati al di fuori della directory di destinazione prevista, con conseguente compromissione dell'integrità del filesystem interessato. La vulnerabilità identificata tramite la CVE-2026-88044, associata a una vulnerabilità di tipo "Authentication Bypass" e con CVSS 3.1 pari a 9.1, è dovuta a un'errata gestione delle configurazioni auth-proxy per i servizi FTP e S3 avviati tramite l'interfaccia Remote Control (RC) di rclone. Un attaccante remoto non autenticato potrebbe sfruttare tale vulnerabilità inducendo il servizio a ignorare i controlli di autenticazione configurati dall'amministratore e ad utilizzare modalità operative di fallback meno restrittive, ottenendo accesso non autorizzato alle funzionalità di lettura, scrittura o cancellazione dei dati esposti e causando la compromissione della riservatezza e dell'integrità delle informazioni trattate. La vulnerabilità identificata tramite la CVE-2026-88017, di tipo "Authorization Bypass" e con CVSS 3.1 pari a 7.3, è dovuta a una gestione non corretta delle credenziali associate alle sessioni FTP autenticate tramite auth-proxy. Un attaccante autenticato potrebbe sfruttare tale vulnerabilità stabilendo sessioni concorrenti che condividono lo stesso nome utente al fine di provocare una sovrapposizione delle credenziali memorizzate dal server e ottenere accesso non autorizzato alle risorse associate a un backend differente, con possibilità di leggere, modificare, rinominare o cancellare dati appartenenti ad altri utenti.

Official advisory ↗
03

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.
Patch available
Affected
rclone: >= 1.75.0, < 1.75.1
Fixed
1.75.1.
Action
Review the linked authoritative reference and apply the recorded fixed release appropriate to the affected product branch.
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 10 Sept 2026 · Last source change 10 Sept 2026, 17:31 UTC · CWE-789 · Memory Allocation with Excessive Size Value

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 2026-09-11
European sourceENISA EUVD · EUVD-2026-75588
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceCNA
NVD statusNVD awaiting enrichment

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

Material change intelligence

What changed after publication

View recent updates ↗
  1. ENISA EUVD mappingEUVD-2026-75588 was added to the official ENISA EUVD mapping for this CVE.
    Before
    not recorded
    After
    {"euvdId":"EUVD-2026-75588"}
    ENISA EUVD ↗
  2. Public exploit evidencePublic exploit evidence changed from No public exploit to Public exploit reference.
    Before
    No public exploit
    After
    Public exploit reference
    CVE.org ↗
  3. Catalogue recordCVE added to the BlackTree catalogue.
    CNA ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
ENISA EUVD · EUVD-2026-75588↗Vendor CSAF · Red Hat Product Security↗CISA Vulnrichment SSVC evidence↗CVE authority or vendor reference · GitHub GHSA-2P48-J3QC-RX9F↗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.
Free version - for non-commercial use only.CVE-2026-88045 · cve.blacktree.nl