CVE-2014-3931
CVE-2014-3931 is a security flaw in Looking Glass Multi-Router Looking Glass (MRLG). Attackers can corrupt memory in Looking Glass Multi-Router Looking Glass (MRLG), which they use to take it over. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 7 Jul 2025.[1]
Looking Glass Multi-Router Looking Glass (MRLG) 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. Looking Glass has published a fix or advice.
Description
CISA calls it a buffer overflow in Looking Glass Multi-Router Looking Glass (MRLG). In its words: “Multi-Router Looking Glass (MRLG) contains a buffer overflow vulnerability that could allow remote attackers to cause an arbitrary memory write and memory corruption.”[1]
The underlying weakness is memory buffer error (CWE-119), 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; Looking Glass’s advisory has them[3]. CISA names the product as Looking Glass Multi-Router Looking Glass (MRLG).
Most families won’t have Looking Glass Multi-Router Looking Glass (MRLG); it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 7 Jul 2025, 3,020 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 28 Jul 2025 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 29%. That’s in the top 2% 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
Looking Glass has published a fix or advice.[3] CISA’s required action: “Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.”[1]
- Check whether you use it.Looking Glass Multi-Router Looking Glass (MRLG) 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 28 Jul 2025 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 29%.[4] |
See also
Other memory buffer error flaws
- CVE-2026-88779, Citrix NetScaler: improper restriction of operations within the bounds of a memory buffer ·
- CVE-2026-88772, Citrix NetScaler: improper restriction of operations within the bounds of a memory buffer ·
- CVE-2026-88771, Citrix NetScaler: improper input validation ·
- CVE-2026-8452, Citrix NetScaler ADC and NetScaler Gateway: improper restriction of operations within the bounds of a memory buffer ·
- CVE-2009-3459, Adobe Acrobat and Reader: heap-based buffer overflow ·
Added the same day
- CVE-2019-9621, Synacor Zimbra Collaboration Suite (ZCS): server-side request forgery (SSRF) ·
- CVE-2019-5418, Rails Ruby on Rails: path traversal ·
- CVE-2016-10033, PHPMailer: command injection ·
References
- ^ Cybersecurity and Infrastructure Security Agency. “Multi-Router Looking Glass (MRLG) Buffer Overflow Vulnerability”. Known Exploited Vulnerabilities Catalog, added 7 Jul 2025.
- ^ National Institute of Standards and Technology. “CVE-2014-3931 Detail”. National Vulnerability Database, published 31 Mar 2017.
- ^ Looking Glass. Advisories and fixes: mrlg.op-sec.us.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.290, percentile 98.2, 31 Oct 2026.
- CVE Program. “CVE-2014-3931”. 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.