Authenticated server crash via unchecked block remainder
Published Dec 14, 2025 · Updated Dec 14, 2025
Improper quantity validation in OpenRsync 0 through 0.5.0 allows remote authenticated users to crash a server via crafted block data. In blk_send_ack(), a short-circuit condition skips comparison of p->rem with p->len when p->len is zero, allowing downloader.c to use an oversized remainder as a copy length. The attacker must complete an rsync protocol exchange and reach receiver-side processing; successful exploitation terminates the process with SIGSEGV and interrupts the transfer.
Summary
What happened
Improper quantity validation in OpenRsync 0 through 0.5.0 allows remote authenticated users to crash a server via crafted block data. In blk_send_ack(), a short-circuit condition skips comparison of p->rem with p->len when p->len is zero, allowing downloader.c to use an oversized remainder as a copy length. The attacker must complete an rsync protocol exchange and reach receiver-side processing; successful exploitation terminates the process with SIGSEGV and interrupts the transfer.
The record
- CVE
- CVE-2025-67901
- Published
- Dec 14, 2025
- Updated
- Dec 14, 2025
- Vendor
- Kristaps Dzonsons
- Product
- OpenRsync
- Classifications
- CWE-1284, T1499.004
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Dec 14, 2025CVE publishedPublication date reported by the CVE source.
- Dec 14, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=0 <=0.5.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- OpenRsync malformed block metadata proof of conceptproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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