CVE-2024-45519
CVE-2024-45519 is a security flaw in Synacor Zimbra Collaboration Suite (ZCS), email and calendar software companies run on their own servers. Attackers can run commands on Synacor Zimbra Collaboration Suite (ZCS) from anywhere, without logging in. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 3 Oct 2024.[1]
Synacor Zimbra Collaboration Suite (ZCS) is business software or equipment. Most families won’t have it, but attackers break into it to get inside companies, and from there to what those companies hold about their customers, patients and staff. Synacor has published a fix or advice.
Description
CISA calls it a command execution in Synacor Zimbra Collaboration Suite (ZCS). In its words: “Synacor Zimbra Collaboration Suite (ZCS) contains an unspecified vulnerability in the postjournal service that may allow an unauthenticated user to execute commands.”[1]
The underlying weakness is improper access control (CWE-284), in MITRE’s list of common software weaknesses.[2]
It scores 9.8 out of 10 on the Common Vulnerability Scoring System, which rates it critical, scored by NVD using CVSS 3.1.[2]
Affected versions
NVD’s record doesn’t list version ranges for it; Synacor’s advisory has them[3]. CISA names the product as Synacor Zimbra Collaboration Suite (ZCS).
Most families won’t have Synacor Zimbra Collaboration Suite (ZCS); it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 3 Oct 2024, within a day of it being made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 24 Oct 2024 to fix it.[1]
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at over 99%. That’s in the top 1% of the flaws it scores.[4]
CISA assesses it as automatable: attackers can run it against many targets at once.
CISA doesn’t say who was attacked, or how.
Fix
Synacor has published a fix or advice.[3] CISA’s required action: “Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.”[1]
- Check whether you use it.Synacor Zimbra Collaboration Suite (ZCS) is business software or equipment, so most families won’t have it. If you run a business, or work from home on company equipment, ask whoever looks after your IT.
- Send this page to your IT person.Ask them to confirm it’s fixed, or not in use. CISA gave US government agencies until 24 Oct 2024 to fix it.
- If it can’t be fixed, take it offline.CISA’s advice when there’s no fix is to stop using the product, or take it off the internet, until there is one.
You can’t fix someone else’s server, but you can watch for what follows a break-in like this: a breach notice, a password reset you didn’t ask for, or a scam message that knows things it shouldn’t. HARD watches for those for you and your family.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 9.8.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at over 99%.[4] |
See also
Other Synacor Zimbra Collaboration Suite (ZCS) flaws
- CVE-2026-73570: OS command injection ·
- CVE-2025-48700: cross-site scripting ·
- CVE-2025-66376: cross-site scripting ·
- CVE-2025-68645: PHP remote file inclusion ·
- CVE-2025-27915: cross-site scripting ·
- CVE-2019-9621: server-side request forgery (SSRF) ·
Other Synacor flaws
- CVE-2020-7796, Synacor Zimbra Collaboration Suite: (ZCS) server-side request forgery ·
- CVE-2022-24682, Synacor Zimbra Collaborate Suite (ZCS): cross-site scripting ·
Other improper access control flaws
- CVE-2015-3306, ProFTPD: improper access control ·
- CVE-2026-21962, Oracle HTTP Server and Oracle Weblogic Server Proxy Plug-in: improper access control ·
- CVE-2026-56290, Joomlack Page Builder: improper access control ·
- CVE-2026-34908, Ubiquiti UniFi OS: improper access control ·
- CVE-2026-48907, Widget Factory Joomla Content Editor: improper access control ·
Every Synacor flaw on CISA’s list · Everything added in October 2024
References
- ^ Cybersecurity and Infrastructure Security Agency. “Synacor Zimbra Collaboration Suite (ZCS) Command Execution Vulnerability”. Known Exploited Vulnerabilities Catalog, added 3 Oct 2024.
- ^ National Institute of Standards and Technology. “CVE-2024-45519 Detail”. National Vulnerability Database, published 2 Oct 2024.
- ^ Synacor. Advisories and fixes: wiki.zimbra.com, wiki.zimbra.com, wiki.zimbra.com, wiki.zimbra.com, wiki.zimbra.com, and 1 more on NVD’s record.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.999, percentile 100.0, 31 Oct 2026.
- CVE Program. “CVE-2024-45519”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.