CVE-2026-20128
CVE-2026-20128 is a security flaw in Cisco Catalyst SD-WAN Manager, Cisco’s business networking equipment. Attackers can read information from Cisco Catalyst SD-WAN Manager that should be private 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 20 Apr 2026.[1]
Cisco Catalyst SD-WAN Manager 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 storing passwords in a recoverable format in Cisco Catalyst SD-WAN Manager. In its words: “Cisco Catalyst SD-WAN Manager contains a storing passwords in a recoverable format vulnerability that allows an authenticated, local attacker to gain DCA user privileges by accessing a credential file for the DCA user on the filesystem as a low-privileged user.”[1]
The CVE record adds: “A vulnerability in the Data Collection Agent (DCA) feature of Cisco Catalyst SD-WAN Manager could allow an unauthenticated, remote attacker to gain DCA user privileges on an affected system. This vulnerability is due to the presence of a credential file for the DCA user on an affected system. An attacker could exploit this vulnerability by sending a crafted HTTP request and reading the file that contains the DCA password from that affected system. A successful exploit could allow the attacker to access another affected system and gain DCA user privileges. Note: Cisco Catalyst SD-WAN Manager releases 20.18 and later are not affected by this vulnerability.”[2]
The underlying weakness is CWE-257, in MITRE’s list of common software weaknesses.
It scores 7.5 out of 10 on the Common Vulnerability Scoring System, which rates it high, 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 Catalyst SD-WAN Manager.
Most families won’t have Cisco Catalyst SD-WAN Manager; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 20 Apr 2026, 54 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 23 Apr 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 7%. That’s in the top 6% of the flaws it scores.[4]
CISA assesses it as not automatable: each attack takes some work.
CISA doesn’t say who was attacked, or how.
Fix
Cisco has published a fix or advice.[3] CISA’s required action: “Please adhere to CISA’s guidelines to assess exposure and mitigate risks associated with Cisco SD-WAN devices as outlines in CISA’s Emergency Directive 26-03 (URL listed below in Notes) and CISA’s “Hunt & Hardening Guidance for Cisco SD-WAN Devices (URL listed below in Notes).”[1]
- Check whether you use it.Cisco Catalyst SD-WAN Manager 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 23 Apr 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 7.5.[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 7%.[4] |
See also
Other Cisco Catalyst SD-WAN Manager flaws
- CVE-2026-76504: hex encoding ·
- CVE-2026-20262: directory or path traversal ·
- CVE-2026-20245: improper encoding or escaping of output ·
- CVE-2026-20133: exposure of sensitive information to an unauthorized actor ·
Other Cisco flaws
- CVE-2026-76418, Cisco Secure Firewall ASA Software and Cisco Secure FTD Software: unchecked return value to NULL pointer dereference ·
- CVE-2026-76519, Cisco Secure Email Gateway: relative path traversal ·
- CVE-2026-76460, Cisco Identity Services Engine: incorrect use of privileged APIs ·
- CVE-2026-76461, Cisco Secure Email Gateway: SQL injection ·
- 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 ·
Added the same day
- CVE-2026-20133, Cisco Catalyst SD-WAN Manager: exposure of sensitive information to an unauthorized actor ·
- CVE-2026-20122, Cisco Catalyst SD-WAN Manger: catalyst SD-WAN manager incorrect use of privileged APIs ·
- CVE-2025-48700, Synacor Zimbra Collaboration Suite (ZCS): cross-site scripting ·
- CVE-2025-32975, Quest KACE Systems Management Appliance (SMA): improper authentication ·
- CVE-2025-2749, Kentico Xperience: xperience path traversal ·
Every Cisco flaw on CISA’s list · Everything added in April 2026
References
- ^ Cybersecurity and Infrastructure Security Agency. “Cisco Catalyst SD-WAN Manager Storing Passwords in a Recoverable Format Vulnerability”. Known Exploited Vulnerabilities Catalog, added 20 Apr 2026.
- ^ National Institute of Standards and Technology. “CVE-2026-20128 Detail”. National Vulnerability Database, published 25 Feb 2026.
- ^ Cisco. Advisories and fixes: sec.cloudapps.cisco.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.073, percentile 94.4, 31 Oct 2026.
- CVE Program. “CVE-2026-20128”. 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.