CVE-2026-70457
Received Received - Intake

Out-of-Bounds Write in rsync 3.2.3

Publication date: 2026-08-13

Last updated on: 2026-08-13

Assigner: VulnCheck

Description
rsync 3.2.3 before 3.5.0 contains an out-of-bounds write in parse_size_arg() where the return value of snprintf() is used directly as an index into a .bss-segment array without bounds checking. When snprintf truncates the formatted size string, the return value equals the number of characters that would have been written including the truncated portion, and this value may exceed the array length. The subsequent indexed write targets memory outside the intended array bounds, corrupting .bss memory.

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Meta Information

Published
2026-08-13
Last Modified
2026-08-13
Generated
2026-08-13
AI Q&A
2026-08-13
EPSS Evaluated
N/A
NVD
CVE-2026-70457
EUVD
EUVD-2026-58047

Affected Vendors & Products

Currently, no data is known.

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-787 The product writes data past the end, or before the beginning, of the intended buffer.
CWE-131 The product does not correctly calculate the size to be used when allocating a buffer, which could lead to a buffer overflow.

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Executive Summary

CVE-2026-70457 is an out-of-bounds write vulnerability in rsync versions 3.2.3 through 3.4.4. It occurs in the parse_size_arg() function when snprintf() truncates a size string and its return value (including truncated characters) is used as an index for a .bss-segment array without bounds checking. This causes a two-byte write at a controlled offset, corrupting memory outside the intended array bounds.

Detection Guidance

Check rsync version with 'rsync --version' to see if it is between 3.2.3 and 3.4.4. Monitor logs for crashes or memory corruption errors during rsync operations, especially when using options like --max-size, --min-size, --max-alloc, --bwlimit, or --block-size.

Impact Analysis

This vulnerability could allow attackers to corrupt memory on systems running vulnerable rsync versions. If options like --max-size are forwarded to a daemon, remote exploitation is possible. While the fixed bytes limit impact to memory corruption rather than arbitrary code execution, it may still cause crashes or instability in affected systems.

Mitigation Strategies

Upgrade rsync to version 3.5.0 or later immediately. If upgrading is not possible, disable rsync daemon mode or restrict access to rsync services until patched. Avoid using vulnerable options in rsync commands.

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