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CVE Record

CVE-2026-29518: Rsync < 3.4.3 TOCTOU Race Condition Allows Symlink-Based Arbitrary File Write

Rsync versions before 3.4.3 contain a time-of-check to time-of-use (TOCTOU) race condition in daemon file handling that allows attackers to redirect file writes outside intended directories by replacing parent directory components with symbolic links. Attackers with write access to a module path can exploit this race condition to create or overwrite arbitrary files, potentially modifying sensitive system files and achieving privilege escalation when the daemon runs with elevated privileges. This vulnerability can only be triggered if the chroot setting is false.

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

Rsync before 3.4.3 has a race condition that can let a user who can write into an rsync daemon module redirect writes outside the intended directory. The biggest business risk is privilege escalation or sensitive file overwrite when rsyncd runs with elevated privileges and chroot is disabled.

Executive priority

Prioritize patching and configuration review on servers that expose writable rsync daemon modules. This is not a broad unauthenticated internet worm scenario from the provided evidence, but the potential file-write impact justifies high urgency on exposed privileged deployments.

Technical view

The flaw is a CWE-367 TOCTOU race in rsync daemon file handling. If chroot is false, an attacker with write access to a module path may replace parent directory components with symbolic links between check and use, causing rsync to write outside the module boundary. Successful exploitation depends on winning the race.

Likely exposure

Highest exposure is rsync daemon deployments before 3.4.3 with writable modules, chroot set to false, and elevated daemon privileges. Systems using vendor-packaged rsync should verify vendor advisory status because the affected-version metadata in the bundle is sparse.

Exploitation context

The source bundle does not show CISA KEV listing or cited evidence of active exploitation. Exploitation requires prior write access to an rsync module path and a timing race, but impact can be severe if writes reach sensitive files.

Researcher notes

Focus analysis on the daemon path-handling race, chroot=false prerequisite, writable module requirement, and privilege context. The provided affected-product metadata appears incomplete, so validate against upstream release notes and vendor advisories before making fleet-wide assumptions.

Mitigation direction

  • Upgrade rsync to 3.4.3 or vendor-fixed packages.
  • Apply relevant Red Hat security errata where applicable.
  • Review rsync daemon modules with chroot set to false.
  • Restrict write access to rsync module paths.
  • Run rsync daemon with least necessary privileges.
  • Check current vendor guidance for platform-specific remediation.

Validation and detection

  • Inventory systems running rsync daemon versions before 3.4.3.
  • Identify modules that allow writes from users or automation accounts.
  • Review rsync daemon configuration for chroot set to false.
  • Confirm installed packages match fixed vendor advisory versions.
  • Assess whether daemon privileges could overwrite sensitive files.
  • Document compensating controls where immediate patching is delayed.
Prepared
Confidence
medium
Sources
12

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

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-367: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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description · low confidence lookup

Privilege behavior lookup

The CVE wording references privilege impact, so privilege escalation and authorization behavior review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

Open ATT&CK lookup
description · low confidence lookup

File access behavior lookup

The CVE wording references file access or upload behavior, so file telemetry and web shell review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2026-29518 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.8 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H

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.

3CVSS vectors
5Timeline events
2ADP providers
12Source links

SSVC decision data

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

CVSS vector scores

3 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
7.8CVSS 3.1HighCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H1.16redhat-SADP
7.3CVSS 4.0HighCVSS:4.0/AV:L/AC:H/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N——VulnCheck
7CVSS 3.1HighCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H15.9VulnCheck

Vulnerability scoring details

Base CVSS 4.0 score

7.3High
CVSS 4.0 vector shape for CVE-2026-29518Attack VectorAttack ComplexityAttack RequirementsPrivileges RequiredUser InteractionVS ConfidentialityVS IntegrityVS AvailabilitySS ConfidentialitySS IntegritySS Availability

Vector: CVSS:4.0/AV:L/AC:H/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/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. ADP timelineredhat-SADP

    Reported to Red Hat.

  3. ADP timelineredhat-SADP

    Made public.

  4. CVE publishedCVE Program

    The CVE record was published.

  5. CVE updatedCVE Program

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

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPrsync: TOCTOU symlink race condition allowing local privilege escalation in daemon mode without chroot.
other:Red Hat severity ratingcvssV3_1
  • 2026-05-11T13:09:31.417Z: Reported to Red Hat.
  • 2026-05-20T00:00:00.000Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
RsyncProjectrsync0unaffected
Weakness

CWE details

CWE-367

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

CWE-367 · source CWE mapping

Time-of-check Time-of-use (TOCTOU) Race Condition

Time-of-check Time-of-use (TOCTOU) Race Condition represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs