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Cisco ios, improper restriction of operations within the bounds of a memory buffer: 11 records, one defect family

Cisco ios has been reported 11 separate times for the same kind of mistake, CWE-119, between 2017-07-17 and 2026-08-05. A defect family is our own grouping of the CVE corpus: every record naming one product and one weakness class, collected so a repeat is visible as a repeat. No public source publishes this, and what this page counts is how often this one product has gone wrong in this one way.

What this page is, and what it is not

The records are public. This grouping is not, and this one took more than a lookup. Every record here carries CWE-119, which matches exactly. The product name does not: the authorities wrote it 2 different ways, and no text match joins those strings, so a search for any one spelling finds a fraction of what exists and gives no sign the rest is there. Our own embedding, pro@dim2000, read those 2 groups, of 6, 5 records, and found they name one product. That is how 11 records no public source connects came to be on one page, and it is the part you cannot look up. Every spelling stays printed beside its own records, because a judgement you cannot inspect is a judgement you should not cite, and if one of them is a different product this family is wrong and its count is wrong with it.

One record is an incident. 11 filings, between 2017-07-17 and 2026-08-05, all landing on the same weakness class in the same product, is a habit in what gets reported here, and a habit is something you can plan around. This is what we held on 2026-09-20.

A repeat is evidence about where to look. If you are reviewing Cisco ios, the records below say which mistake has already been found more than once, which is the cheapest place a reviewer can start. If you are asking the vendor a question, a count under one weakness class is a better question than any single record is.

What this page cannot tell you is decided by what was joined. A product name and a weakness class settled membership, so those two values are the whole of what the page asserts. Records here may sit in the same line of code or in unrelated parts of the product, and we hold no value that separates those cases. A fixed version named in one record closes that record and says nothing about the others. And nothing here describes anyone's systems, because no value in this family connects a product name to an installation.

CVE-2017-6736CVE-2017-6737CVE-2017-6738CVE-2017-6740CVE-2017-6743CVE-2017-6744CVE-2017-6741CVE-2017-6742CVE-2021-1433CVE-2021-1451CVE-2026-20268
This family is two groups, 6 records and 5 between 2017-07-17 and 2026-08-05. Neither accounts for most of it, and nothing in the product name said they were the same defect family.

The names the authorities used

2 different ways, each written by whoever filed the records under it. They are printed as written rather than tidied, because the tidying is the step that would hide what was merged.

cisco ios
cisco ios xe software

Family membership: computed, pro@dim2000

What pulled them together

These records reached one family from 2 separate groups. A join on the product name alone could not see they were the same, because the authorities wrote the product and its versions differently each time. The grouping was computed by pro@dim2000.

6 recordsCVE-2017-6736, CVE-2017-6737, CVE-2017-6738, CVE-2017-6740, CVE-2017-6743, CVE-2017-6744
5 recordsCVE-2017-6741, CVE-2017-6742, CVE-2021-1433, CVE-2021-1451, CVE-2026-20268

What the records offer

No record in this family publishes a fixed version in held sources.

7 records are listed by CISA with a required action, which carries a federal remediation deadline on its own page.

The earliest was published 2017-07-17 and the latest 2026-08-05. That span is how long this product kept producing this weakness, not how long any one record took to fix.

What this family was researched, not held

One SNMP advisory in 2017 supplied most of this grouping

Eight of these records came out of a single Cisco advisory published on 29 June 2017, which covered nine identifiers and gave them one cause: a buffer overflow in the SNMP subsystem of IOS and IOS XE. The reach came from data, not from code paths, since the overflow was reachable through any of ten named management information bases and through SNMP versions 1, 2c and 3. Cisco's incident response team recorded that it was aware of exploitation of eight of the nine, and that exploit code was available for CVE-2017-6741. Because a patch was not immediately available for every release, the advisory's workaround was a configuration list: allow only trusted users SNMP access, and exclude each of the ten vulnerable management information bases from SNMP views. The later records in this grouping are different software, including a 2021 SD-WAN daemon and a 2021 switching feature, and an August 2026 IOS XE hardening release that Cisco says came from its own internal testing, using existing processes and frontier AI models, with no known malicious use.

The repeating fault is a parser writing past the end of a buffer, and the 2017 set shows how far one such parser reaches when it sits behind a management protocol. Reachability mattered as much as version there: the fix list was patches, but the stopgap was restricting who could talk SNMP to the device and which data objects they could ask for. Each record carries its own advisory and its own fixed release.

2017-06-29Cisco publishes one SNMP advisory covering CVE-2017-6736 through CVE-2017-6744, giving a single cause, a buffer overflow in the SNMP subsystem…
2017-06-29The same advisory records that Cisco's incident response team is aware of exploitation of eight of the nine identifiers, and that exploit code is…
2022-03-03CISA adds CVE-2017-6736 to the Known Exploited Vulnerabilities catalog as a Cisco IOS and IOS XE Software SNMP Remote Code Execution Vulnerability.
2023-04-19CISA adds CVE-2017-6742 to the same catalog, more than a year after its siblings.
2026-08-05Cisco publishes an IOS XE security hardening release covering CVE-2026-20267 through CVE-2026-20273, found by internal testing using existing…

This note does not establish that these records share a vulnerability, a fix or a device estate, even where they were published on the same day. They were grouped because they read alike, and remediating one of them does not address any other.

Written from cisco.com, cisa.gov, cisco.com. Stated at high confidence. Nothing in this box is a value the index holds, and none of it opens a receipt.

What this page does not cover

This is a family of records that read alike. It is not a shared vulnerability, not an inventory, and not a statement that one fix closes the rest. Each record's own state, its own dates and its own receipts are on its own page.

Grouped by shared product and weakness, not by shared vulnerability. Each record's own state is on its own page.

Everything this vendor has, including records outside this family:

CVE-2017-6736no title heldCWE-119 Improper Restriction of Operations…
CVE-2017-6737no title heldCWE-119 Improper Restriction of Operations…
CVE-2017-6738no title heldCWE-119 Improper Restriction of Operations…
CVE-2017-6740no title heldCWE-119 Improper Restriction of Operations…
CVE-2017-6741no title heldCWE-119 Improper Restriction of Operations…
CVE-2017-6742no title held
CVE-2017-6743no title heldCWE-119 Improper Restriction of Operations…
CVE-2017-6744no title heldCWE-119 Improper Restriction of Operations…
CVE-2021-1433Cisco IOS XE SD-WAN Software vDaemon Buffer Overflow VulnerabilityCWE-119
CVE-2021-1451Cisco IOS XE Software Easy Virtual Switching System Arbitrary Code Execution VulnerabilityCWE-119
CVE-2026-20268Cisco IOS XE Software Security Hardening ReleaseCWE-119 Improper Restriction of Operations…

11 records, read from the index as it stood on 20 Sep 2026. Every row opens the record it names, and every value on that record opens its own receipt.

Everything on this page is free. Public data. Withholding it protects nothing.