Alibaba Cloud Linux 3 : 0323: rsync (ALINUX3-SA-2026:0323)

critical Nessus Plugin ID 373499

Synopsis

The remote Alibaba Cloud Linux host is missing one or more security updates.

Description

The remote Alibaba Cloud Linux 3 host has packages installed that are affected by multiple vulnerabilities as referenced in the ALINUX3-SA-2026:0323 advisory.

Package updates are available for Alibaba Cloud Linux 3 that fix the following vulnerabilities:

CVE-2026-53783:
rsync before3.5.0 contains a time-of-check to time-of-use (TOCTOU) race condition vulnerability in the rrsync restricted shell wrapper that allows authenticated clients to escape enforced directory restrictions by substituting a symlink for a path component after validation but before transfer processing. Attackers can additionally leverage unrestricted flags such as --copy-unsafe-links, -D, and
--log-file through rrsync to read or write files outside the permitted directory subtree.

CVE-2026-53784:
rsync before 3.5.0contains a path traversal vulnerability that allows remote clients to access files outside the intended module root when use chroot is disabled and the module root path or a component of it is a symlink. The daemon calls chdir() to the module root at session initialization without resolving symlinks via realpath() or equivalent, causing subsequent relative-path operations to reference files relative to the symlink target rather than the intended module root, enabling unauthorized file access.

CVE-2026-53785:
rsyncbefore 3.5.0contains a path traversal vulnerability that allows a malicious sender to write files outside the intended destination directory tree by crafting relative paths with symlink components in
--relative mode. The make_path() function follows symlinks pointing outside the destination tree while creating intermediate directories without verifying that created paths remain within the destination boundary, enabling arbitrary file writes on the receiver's filesystem.

CVE-2026-53789:
rsync before 3.5.0contains an improper path handling vulnerability that allows a malicious sender to expand the scope of --delete operations beyond the intended destination subtree by sending a crafted file list that causes rsync to reclassify implied parent directory entries or treat synthetic paths as the transfer root. Attackers can exploit multiple variants including implied parent reclassification, synthetic root path construction, legacy protocol behavior below version 30, and non-directory root handling to cause the receiver to delete files outside the authorized destination directory.

CVE-2026-53790:
rsync before 3.5.0contains multiple command and argument injection vulnerabilities that allow attackers to execute arbitrary commands by supplying malicious input through several code paths, including the RSYNC_CONNECT_PROG environment variable, daemon hooks, the rsync-ssl wrapper, and remote-shell command newline injection. Attackers can inject shell metacharacters or newline characters into unsanitized user- supplied values such as hostnames and hostspecs to execute arbitrary commands under the privileges of the rsync process or the invoking user.

CVE-2026-53793:
rsync before 3.5.0contains 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.

CVE-2026-53795:
rsync before 3.5.0contains an arbitrary file write vulnerability that allows attackers to write files outside the intended destination tree by specifying an absolute path via --temp-dir or --link-dest options. The rename-confinement logic is bypassed when these options resolve to paths outside the destination tree, enabling attacker-controlled values to write files to arbitrary locations accessible to the rsync process.

CVE-2026-53802:
rsync before 3.5.0 contains an arbitrary file read vulnerability that allows attackers to read files accessible to the rsync daemon process by exploiting symlink following in input configuration file handling including --files-from, --password-file, and filter merge files. Attackers can place a symlink at a predictable --files-from or --password-file path, or supply a --files-from path that escapes the daemon module root, to read arbitrary files accessible to the rsync process.

CVE-2026-53803:
rsync before 3.5.0 contains a symlink following vulnerability that allows local attackers to overwrite arbitrary files by placing a symlink at a predictable output path such as --log-file, --write-batch, or daemon-mode log and statistics paths. Attackers can exploit rsync's failure to reject symlinks during ancillary file writes to redirect output to arbitrary filesystem locations, achieving local privilege escalation on installations where rsync runs with elevated privileges such as setuid or privileged daemon configurations.

CVE-2026-70452:
rsync 3.1.0 before 3.5.0 contains an access control bypass vulnerability that allows remote attackers to circumvent hosts deny rules by inducing DNS resolution failures during hostname-based access control evaluation. When a DNS lookup for a hostname-based deny rule fails, the daemon skips the rule rather than defaulting to a deny decision, enabling attackers who can trigger DNS failures to bypass module-level IP access controls and gain unauthorized access to restricted module file trees.

CVE-2026-70453:
rsync before 3.5.0contains an algorithmic complexity vulnerability in the hash_search() function that allows a remote attacker to cause a denial of service by delivering a carefully constructed file list. A sender can exploit the quadratic-time worst-case behavior in hash lookups to exhaust receiver CPU resources with a modest number of crafted entries, causing a sustained denial of service.

CVE-2026-70456:
rsync 3.0.1 before 3.5.0contains an out-of-bounds write vulnerability in the read_args() function that allows a malicious sender to corrupt adjacent heap memory by sending a crafted argument list. When the argument count causes the argv allocation to be exactly full, the trailing NULL terminator is written one slot beyond the allocation boundary, corrupting adjacent heap memory.

CVE-2026-70458:
rsync 3.0.0 before 3.5.0 contains an out-of-bounds write vulnerability that allows attackers to corrupt memory by triggering HLINK_BUMP processing on file entries with the FLAG_HLINKED flag set while the hard- link preservation option is inactive. Attackers can exploit the missing F_SUM field in the file_struct layout to access memory past the end of the allocated structure, corrupting adjacent heap or stack data.

CVE-2026-70460:
rsync 2.3.3 before 3.5.0contains a path traversal vulnerability that allows a malicious sender to escape the module root by exploiting symlinks within the module file tree when using --partial-dir or --backup- dir options. Attackers with write access to place a symlink under the module root, or who can exploit a pre-existing trusted symlink, can direct file writes to locations outside the intended module root, achieving arbitrary file write relative to the module root parent.

CVE-2026-70461:
rsync 3.2.5 before 3.5.0contains a heap out-of-bounds write vulnerability that allows remote unauthenticated attackers to write one attacker-controlled byte past the end of a heap allocation by supplying a crafted files-from entry. Attackers can trigger the vulnerability against a read-only rsync daemon module by providing a files-from entry containing both an interior and trailing backslash, causing the add_implied_include() function to under-count the trailing backslash when sizing the destination buffer.

CVE-2026-70463:
rsync 3.1.0 before 3.5.0contains an authorization bypass in auth users directive parsing. The auth users parser uses comma-only tokenization when splitting the user list, which fails to correctly handle entries of the form @Group Name where the group name contains a space. The space within the group name causes the parser to split the entry at the space boundary, discarding the deny rule associated with the group. An authenticated user whose username or group membership would be denied by an @Group Name auth users entry can connect to a restricted module because the deny rule is silently discarded during parsing.

CVE-2026-70464:
rsync daemon 2.0.0 before 3.5.0contains a denial of service vulnerability that allows unauthenticated remote attackers to exhaust daemon connection slots by stalling the handshake process before or after module selection without triggering the I/O timeout. Attackers can open many simultaneous connections and trickle data at the minimum rate to avoid timeout, or stall entirely before module selection where no timeout applies, consuming all available connection slots and denying service to legitimate clients.

Tenable has extracted the preceding description block directly from the Alibaba Cloud Linux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

Solution

Update the affected rsync, rsync-daemon and / or rsync-doc packages.

Plugin Details

Severity: Critical

ID: 373499

File Name: alinux3_sa_2026-0323.nasl

Version: 1.1

Type: Local

Family: Alibaba Cloud Linux Local Security Checks

Published: 10/29/2026

Updated: 10/29/2026

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 4.9

Percentile: 58.18

CVSS v2

Risk Factor: High

Base Score: 9.4

Temporal Score: 7.4

Vector: CVSS2#AV:N/AC:L/Au:N/C:N/I:C/A:C

CVSS Score Source: CVE-2026-53789

CVSS v3

Risk Factor: High

Base Score: 8.1

Temporal Score: 7.3

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H

Temporal Vector: CVSS:3.0/E:P/RL:O/RC:C

CVSS v4

Risk Factor: Critical

Base Score: 9.2

Threat Score: 8.2

Threat Vector: CVSS:4.0/E:P

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

CVSS Score Source: CVE-2026-70460

Vulnerability Information

CPE: cpe:/o:alibabacloud:alibaba_cloud_linux_3, p-cpe:/a:alibabacloud:alibaba_cloud_linux_3:rsync-daemon, p-cpe:/a:alibabacloud:alibaba_cloud_linux_3:rsync-doc, p-cpe:/a:alibabacloud:alibaba_cloud_linux_3:rsync

Required KB Items: Host/local_checks_enabled, Host/cpu, Host/Alibaba/release, Host/Alibaba/rpm-list

Exploit Available: true

Exploit Ease: Exploits are available

Patch Publication Date: 10/28/2026

Vulnerability Publication Date: 8/13/2026

Reference Information

CVE: CVE-2026-53783, CVE-2026-53784, CVE-2026-53785, CVE-2026-53789, CVE-2026-53790, CVE-2026-53793, CVE-2026-53795, CVE-2026-53802, CVE-2026-53803, CVE-2026-70452, CVE-2026-70453, CVE-2026-70456, CVE-2026-70458, CVE-2026-70460, CVE-2026-70461, CVE-2026-70463, CVE-2026-70464

Detections

Analytics