CVE-2023-1671
CVE-2023-1671 is a security flaw in Sophos Web Appliance. Attackers can run their own code on Sophos Web Appliance 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 16 Nov 2023.[1]
Sophos Web Appliance 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. Fixed in version 4.3.10.4 of Sophos Web Appliance.
Description
CISA calls it a command injection in Sophos Web Appliance. In its words: “Sophos Web Appliance contains a command injection vulnerability in the warn-proceed handler that allows for remote code execution.”[1]
The underlying weakness is command injection (CWE-77), 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 lists one fixed version: everything before it is affected.[2]
| Product | Fixed in |
|---|---|
| Sophos Web Appliance | 4.3.10.4 |
Most families won’t have Sophos Web Appliance; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 16 Nov 2023, 226 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 7 Dec 2023 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
Sophos 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.Sophos Web Appliance 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 (fixed in version 4.3.10.4 of Sophos Web Appliance), or not in use. CISA gave US government agencies until 7 Dec 2023 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 Sophos flaws
- CVE-2020-29574, Sophos CyberoamOS: (CROS) SQL injection ·
- CVE-2020-15069, Sophos XG Firewall: buffer overflow ·
- CVE-2022-3236, Sophos Firewall: code injection ·
- CVE-2022-1040, Sophos Firewall: authentication bypass ·
- CVE-2020-25223, Sophos SG UTM: remote code execution ·
Other command injection flaws
- CVE-2026-105134, AhsayCBS: command injection ·
- CVE-2026-96951, Microsoft Windows: command injection ·
- CVE-2016-3081, Apache Struts: command injection ·
- CVE-2026-8037, Progress LoadMaster: command injection ·
- CVE-2025-29635, D-Link DIR-823X: command injection ·
Added the same day
- CVE-2023-36584, Microsoft Windows: mark of the web (MOTW) security feature bypass ·
- CVE-2020-2551, Oracle Fusion Middleware: unspecified ·
Every Sophos flaw on CISA’s list · Everything added in November 2023
References
- ^ Cybersecurity and Infrastructure Security Agency. “Sophos Web Appliance Command Injection Vulnerability”. Known Exploited Vulnerabilities Catalog, added 16 Nov 2023.
- ^ National Institute of Standards and Technology. “CVE-2023-1671 Detail”. National Vulnerability Database, published 4 Apr 2023.
- ^ Sophos. Advisories and fixes: sophos.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 1.000, percentile 100.0, 31 Oct 2026.
- CVE Program. “CVE-2023-1671”. 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.