CVE-2026-76519
CVE-2026-76519 is a security flaw in Cisco Secure Email Gateway, Cisco’s business networking equipment. Attackers can run commands on Cisco Secure Email Gateway 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 14 Oct 2026.[1]
Cisco Secure Email Gateway 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. Cisco has published a fix or advice.
Description
CISA calls it a relative path traversal in Cisco Secure Email Gateway. In its words: “Cisco Secure Email Gateway contains a relative path traversal vulnerability that could allow an unauthenticated, remote attacker to write arbitrary files on the underlying operating system.”[1]
The CVE record adds: “A vulnerability in the Advanced Malware Protection (AMP) feature of Cisco Secure Email Gateway could allow an unauthenticated, remote attacker to write arbitrary files on the underlying operating system. This vulnerability is due to improper handling of email attachments when the file reputation service is enabled. An attacker could exploit this vulnerability by sending an email that contains a crafted attachment through an affected device. A successful exploit could allow the attacker to write arbitrary files and execute commands with root privileges on the underlying operating system.”[2]
The underlying weakness is CWE-23, in MITRE’s list of common software weaknesses.
It scores 9.8 out of 10 on the Common Vulnerability Scoring System, which rates it critical, scored by the organisation that published the CVE using CVSS 3.1.[2]
Affected versions
NVD’s record doesn’t list version ranges for it; Cisco’s advisory has them[3]. CISA names the product as Cisco Secure Email Gateway.
Most families won’t have Cisco Secure Email Gateway; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 14 Oct 2026, 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 17 Oct 2026 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 2%. That’s in the top 18% 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
Cisco has published a fix or advice.[3] CISA’s required action: “Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes).”[1]
- Check whether you use it.Cisco Secure Email Gateway 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 17 Oct 2026 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 2%.[4] |
See also
Other Cisco Secure Email Gateway flaws
- CVE-2026-76461: SQL injection ·
Other Cisco flaws
- CVE-2026-76418, Cisco Secure Firewall ASA Software and Cisco Secure FTD Software: unchecked return value to NULL pointer dereference ·
- CVE-2026-76504, Cisco Catalyst SD-WAN Manager: hex encoding ·
- CVE-2026-76460, Cisco Identity Services Engine: incorrect use of privileged APIs ·
- CVE-2026-20079, Cisco Secure Firewall Management Center (FMC) and Security Cloud Control (SCC) Firewall Management: firewall management center authentication bypass using an alternate path or channel ·
- CVE-2026-20349, Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD): heap inspection ·
Similar flaws
- CVE-2026-34926, Trend Micro Apex One: (on-premise) directory traversal ·
- CVE-2024-27199, JetBrains TeamCity: relative path traversal ·
- CVE-2025-64446, Fortinet FortiWeb: path traversal ·
- CVE-2022-37042, Synacor Zimbra Collaboration Suite (ZCS): authentication bypass ·
- CVE-2021-38163, SAP NetWeaver: unrestricted file upload ·
Added the same day
- CVE-2026-105134, AhsayCBS: command injection ·
- CVE-2026-105133, AhsayCBS: improper authentication ·
- CVE-2026-0322, Palo Alto Networks PAN-OS: code injection ·
Every Cisco flaw on CISA’s list · Everything added in October 2026
References
- ^ Cybersecurity and Infrastructure Security Agency. “Cisco Secure Email Gateway Relative Path Traversal Vulnerability”. Known Exploited Vulnerabilities Catalog, added 14 Oct 2026.
- ^ National Institute of Standards and Technology. “CVE-2026-76519 Detail”. National Vulnerability Database, published 14 Oct 2026.
- ^ Cisco. Advisories and fixes: sec.cloudapps.cisco.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.022, percentile 82.2, 31 Oct 2026.
- CVE Program. “CVE-2026-76519”. 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.