CVE-2026-5950 (GCVE-0-2026-5950)

Vulnerability from cvelistv5 – Published: 2026-05-20 13:10 – Updated: 2026-05-20 13:38
VLAI
Title
Unbounded resend loop in BIND 9 resolver
Summary
An unbounded resend loop vulnerability exists in the BIND 9 resolver state machine during bad-server handling, enabling a remote unauthenticated attacker to cause severe resource exhaustion by sending queries that trigger specific retry conditions. This issue affects BIND 9 versions 9.18.36 through 9.18.48, 9.20.8 through 9.20.22, 9.21.7 through 9.21.21, 9.18.36-S1 through 9.18.48-S1, and 9.20.9-S1 through 9.20.22-S1.
Severity
5.3 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-05-20 13:38 UTC
CWE
  • CWE-606 - Unchecked Input for Loop Condition
Assigner
References
Impacted products
Vendor Product Version CPE status
ISC BIND 9 Affected: 9.18.36 , ≤ 9.18.48 (custom)
Affected: 9.20.8 , ≤ 9.20.22 (custom)
Affected: 9.21.7 , ≤ 9.21.21 (custom)
Affected: 9.18.36-S1 , ≤ 9.18.48-S1 (custom)
Affected: 9.20.9-S1 , ≤ 9.20.22-S1 (custom)
    cpe:2.3:a:isc:bind:*:*:*:*:*:*:*:*
    cpe:2.3:a:isc:bind:*:*:*:*:*:*:*:*
    cpe:2.3:a:isc:bind:*:*:*:*:*:*:*:*
    cpe:2.3:a:isc:bind:*:*:*:*:*:*:*:*
    cpe:2.3:a:isc:bind:*:*:*:*:*:*:*:*
Create a notification for this product.
Date Public
2026-05-20 00:00
Credits
ISC would like to thank Billy Baraja (BielraX) for bringing this vulnerability to our attention.
Show details on NVD website
To clipboard 

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              "url": "https://downloads.isc.org/isc/bind9/9.20.23"
            },
            {
              "tags": [
                "patch"
              ],
              "url": "https://downloads.isc.org/isc/bind9/9.21.22"
            }
          ],
          "solutions": [
            {
              "lang": "en",
              "value": "Upgrade to the patched release most closely related to your current version of BIND 9: 9.18.49, 9.20.23, 9.21.22, 9.18.49-S1, or 9.20.23-S1."
            }
          ],
          "source": {
            "discovery": "EXTERNAL"
          },
          "title": "Unbounded resend loop in BIND 9 resolver",
          "workarounds": [
            {
              "lang": "en",
              "value": "No workarounds known."
            }
          ],
          "x_generator": {
            "engine": "cvelib 1.8.0"
          }
        }
      },
      "cveMetadata": {
        "assignerOrgId": "404fd4d2-a609-4245-b543-2c944a302a22",
        "assignerShortName": "isc",
        "cveId": "CVE-2026-5950",
        "datePublished": "2026-05-20T13:10:19.989Z",
        "dateReserved": "2026-04-09T06:42:23.953Z",
        "dateUpdated": "2026-05-20T13:38:53.211Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.