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CVE Record

CVE-2026-53793: rsync < 3.5.0 Path Confinement Bypass via /./ Boundary Marker in Chroot Mode

rsync before 3.5.0 contains a path confinement bypass vulnerability that allows remote clients to escape the intended inner-module root confinement by constructing paths that resolve outside the chroot boundary when the module root contains a /./ boundary marker. Attackers can exploit improper handling of the /./ notation or forge delta-basis transfers referencing xname paths that cross the /./ boundary to gain unauthorized read or write access to files outside the module's subtree.

CriticalCVSS 9.1Not KEV-listedUpdated
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Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

A remote, unauthenticated client may bypass an rsync module’s intended file boundary and read or modify files outside its permitted subtree. The issue affects rsync before 3.5.0 when chroot confinement uses a module path containing the /./ boundary marker. Confidentiality and integrity impact can be severe, although exploitation requires particular configuration and transfer conditions.

Executive priority

Act immediately on externally reachable systems matching the vulnerable configuration, especially where modules are writable or neighboring files are sensitive. Other rsync deployments should receive rapid inventory and configuration validation. The critical score reflects potential unauthorized file disclosure and modification, but the stated high complexity and prerequisite configuration should guide prioritization rather than delay assessment.

Technical view

rsync mishandles /./ confinement boundaries in chroot mode. Crafted paths, including delta-basis transfers referencing xname paths across that boundary, may resolve beyond the inner module root. The issue is classified as CWE-59 and has CVSS 4.0 score 9.1: network-accessible, unauthenticated, high complexity, with a prerequisite condition and high confidentiality and integrity impact.

Likely exposure

Highest exposure is on remotely reachable rsync services running versions earlier than 3.5.0 with chrooted modules whose roots contain a /./ marker. Deployments without that configuration are not shown as vulnerable by the supplied evidence. Internet exposure, writable modules, and access to sensitive files outside the module subtree increase business risk.

Exploitation context

The supplied record does not establish active exploitation, and the CVE is not listed as KEV. Exploitation is described as remote and unauthenticated but high-complexity, requiring a specific chroot and /./ boundary configuration plus particular path or delta-basis handling. Treat exposed matching deployments urgently without representing exploitation as confirmed.

Researcher notes

The vulnerable boundary is the inner module root represented by /./ inside a chroot path. Two mechanisms are described: improper handling of that notation and delta-basis transfers referencing xname paths across the boundary. The supplied sources identify rsync before 3.5.0 and a release containing the correction; they provide no evidence here of public exploitation or KEV inclusion.

Mitigation direction

  • Upgrade affected rsync installations to version 3.5.0 or later using vendor-supported packages.
  • Prioritize internet-reachable servers and modules permitting write operations.
  • Review vendor guidance before using configuration changes as compensating controls.
  • Restrict untrusted network access until upgrades and configuration review are complete.

Validation and detection

  • Inventory rsync versions and identify every installation earlier than 3.5.0.
  • Review daemon modules for chroot use and roots containing a /./ boundary marker.
  • Confirm whether matching modules are remotely reachable or allow writes.
  • After remediation, verify the running binary and package report version 3.5.0 or later.
  • Review file-access logs for unexpected activity outside intended module subtrees.
Prepared
Confidence
high
Sources
5

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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cwe · low confidence lookup

CWE-59: Exact CWE lookup

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cve · low confidence lookup

CVE-2026-53793 mapping review

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Vulnerability profileCVE Program record
Severity
Critical
CVSS
9.1 (4.0)
Known Exploited
No
Published

Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
3Timeline events
1ADP providers
4Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: total

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
9.1CVSS 4.0CriticalCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N——VulnCheck
7.4CVSS 3.1HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N2.25.2VulnCheck

Vulnerability scoring details

Base CVSS 4.0 score

9.1Critical
CVSS 4.0 vector shape for CVE-2026-53793Attack VectorAttack ComplexityAttack RequirementsPrivileges RequiredUser InteractionVS ConfidentialityVS IntegrityVS AvailabilitySS ConfidentialitySS IntegritySS Availability

Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Attack Requirements
NonePresent
Privileges Required
NoneLowHigh
User Interaction
NonePassiveActive
VS Confidentiality
HighLowNone
VS Integrity
HighLowNone
VS Availability
HighLowNone
SS Confidentiality
HighLowNone
SS Integrity
HighLowNone
SS Availability
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
RsyncProjectrsync0, 3.5.0unaffected
Weakness

CWE details

CWE-59

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.