CVE-2026-43618

Rsync version 3.4.2 and prior contain an integer overflow vulnerability in the compressed-token decoder where a 32-bit signed counter is not checked for overflow, allowing a malicious sender to trigger an overflow that causes the receiver process to read and return data from outside the intended buffer bounds. Attackers can exploit this vulnerability to disclose process memory contents including environment variables, passwords, heap and stack data, and library memory pointers, significantly reducing ASLR effectiveness and facilitating further exploitation.

Weakness

The product reads data past the end, or before the beginning, of the intended buffer.

Affected Software

Name	Vendor	Start Version	End Version
Rsync	Samba	*	3.4.2 (including)
Red Hat Enterprise Linux 10	RedHat	rsync-0:3.4.4-1.el10_2	*
Red Hat Enterprise Linux 8	RedHat	rsync-0:3.1.3-27.el8_10	*
Red Hat Enterprise Linux 9	RedHat	rsync-0:3.2.5-7.el9_8.2	*
Red Hat Enterprise Linux 9	RedHat	rsync-0:3.2.5-7.el9_8.2	*
Red Hat Discovery 2	RedHat	discovery/discovery-ui-rhel9:1782166952	*
Rsync	Ubuntu	devel	*
Rsync	Ubuntu	esm-infra-legacy/trusty	*
Rsync	Ubuntu	esm-infra-legacy/xenial	*
Rsync	Ubuntu	esm-infra/bionic	*
Rsync	Ubuntu	esm-infra/focal	*
Rsync	Ubuntu	esm-infra/xenial	*
Rsync	Ubuntu	jammy	*
Rsync	Ubuntu	noble	*
Rsync	Ubuntu	questing	*
Rsync	Ubuntu	resolute	*
Rsync	Ubuntu	upstream	*

Potential Mitigations

Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
To reduce the likelihood of introducing an out-of-bounds read, ensure that you validate and ensure correct calculations for any length argument, buffer size calculation, or offset. Be especially careful of relying on a sentinel (i.e. special character such as NUL) in untrusted inputs.

https://cwe.mitre.org/data/definitions/540.html

NVD	https://nvd.nist.gov/vuln/detail/CVE-2026-43618
CWE	https://cwe.mitre.org/data/definitions/125.html

Out-of-bounds Read

Weakness

Affected Software

Potential Mitigations

References

CVE-2026-43618

Out-of-bounds Read

Weakness

Affected Software

Potential Mitigations

Related Attack Patterns

References