Security readout for executives and security teams
Plain-English summary
An unauthenticated attacker who can directly reach a vulnerable rsync daemon may impersonate a trusted IP address and bypass network-based access restrictions. This could expose protected files or permit unauthorized changes, depending on the affected rsync module’s permissions. The issue affects rsync versions before 3.5.0.
Executive priority
Treat reachable vulnerable daemons protecting sensitive or writable modules as an immediate remediation priority. Upgrade promptly and reduce direct network exposure while remediation proceeds. Lower priority may be appropriate only after confirming the service is not in daemon mode, is already upgraded, or cannot be reached by an attacker.
Technical view
Rsync daemon versions before 3.5.0 trust a crafted PROXY protocol header sufficiently to use its forged source address for hosts allow/deny decisions. Exploitation requires direct connectivity to the daemon but no credentials or user interaction. The CVSS 4.0 score is 9.1, reflecting potentially high confidentiality and integrity impact without stated availability impact.
Likely exposure
Highest exposure exists where rsync daemon versions before 3.5.0 are reachable from untrusted networks and hosts allow/deny rules provide meaningful protection. Systems not running daemon mode, running 3.5.0 or later, or inaccessible to attackers do not match the described attack conditions. Module permissions determine the potential business impact.
Exploitation context
The bundle does not establish active exploitation, and the CVE is not identified as CISA KEV-listed. Exploitation is remotely reachable, unauthenticated, and low complexity, but requires the attacker to connect directly to the rsync daemon and provide a forged PROXY protocol source address.
Researcher notes
CWE-290 applies because the daemon accepts an asserted network identity for authorization. Exposure assessment should distinguish daemon operation from ordinary rsync client use and document whether IP rules gate read or write access. Available sources support the bypass and fixed release, but provide no evidence here of public exploitation or inclusion in KEV.
Mitigation direction
- Upgrade affected rsync daemon installations to version 3.5.0 or later.
- Until upgraded, restrict daemon connectivity to trusted network paths using controls independent of rsync source-address evaluation.
- Review the vendor advisory and release notes for deployment-specific guidance.
- Confirm sensitive modules enforce authentication and least-privilege read or write permissions.
Validation and detection
- Inventory rsync versions and identify installations earlier than 3.5.0.
- Determine which installations operate in daemon mode and are reachable from untrusted networks.
- Identify modules relying on hosts allow/deny rules for access protection.
- Verify installed versions after remediation and reassess daemon reachability.
- Review access records for unexpected clients or activity involving sensitive modules.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
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-290: 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.
Open ATT&CK lookupCVE-2026-53791 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 9.1 (4.0)
- Known Exploited
- No
- Published
Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
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.
SSVC decision data
CVSS vector scores
2 official scoresWe 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.
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N——VulnCheckCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N3.95.2VulnCheckVulnerability scoring details
Base CVSS 4.0 score
9.1CriticalVector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
Base CVSS 3.1 score
9.1CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- GitHub Security Advisory (GHSA-h2q9-5fr8-w635)CVE reference, VulnCheck · vendor-advisory
- rsync 3.5.0 Release NotesCVE reference, VulnCheck · release-notes
- https://www.vulncheck.com/advisories/rsync-daemon-ip-spoofing-via-proxy-protocol-headerCVE reference, VulnCheck · third-party-advisory
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Authentication Bypass by Spoofing
Authentication Bypass by Spoofing represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.