Vulnerability-Lookup

RHSA-2026:68786

Vulnerability from csaf_redhat - Published: 2026-09-18 00:16 - Updated: 2026-09-18 05:25

Summary

Red Hat Security Advisory: perl-Net-DNS security update

Severity

Important

Notes

Topic: An update for perl-Net-DNS is now available for Red Hat Enterprise Linux 9. Red Hat Product Security has rated this update as having a security impact of Important. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available for each vulnerability from the CVE link(s) in the References section.

Details: The perl-Net-DNS package contains a collection of Perl modules that act as a Domain Name System (DNS) resolver. It allows the programmer to perform DNS queries that are beyond the capabilities of the gethostbyname and gethostbyaddr routines. Security Fix(es): * perl-Net-DNS: Net::DNS: Denial of Service via unbounded recursion with misplaced TSIG records (CVE-2026-81928) For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Terms of Use: This content is licensed under the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/). If you distribute this content, or a modified version of it, you must provide attribution to Red Hat Inc. and provide a link to the original.

CVE-2026-81928

A flaw was found in Net::DNS versions before 1.57 for Perl. An attacker can cause a denial of service (DoS) by sending a specially crafted DNS message with a misplaced Transaction Signature (TSIG) record. When a system using Net::DNS, such as a forwarder or proxy, attempts to re-encode this message, it can lead to unbounded recursion and memory exhaustion, ultimately terminating the process. This vulnerability arises because the `sig_data` function fails to properly remove TSIG records from all sections of a DNS message, violating RFC 8945 section 5.2 requirements.

7.5 (High)


                
                  CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CWE-835 - Loop with Unreachable Exit Condition ('Infinite Loop')

Affected products

Fixed 3 products

Product	Version	Remediation
Unresolved product id: AppStream-9.8.0.Z.MAIN.EUS:perl-Net-DNS-0:1.29-6.el9_8.1.noarch	—	Vendor Fix fix Workaround
Unresolved product id: AppStream-9.8.0.Z.MAIN.EUS:perl-Net-DNS-0:1.29-6.el9_8.1.src	—	Vendor Fix fix Workaround
Unresolved product id: CRB-9.8.0.Z.MAIN.EUS:perl-Net-DNS-Nameserver-0:1.29-6.el9_8.1.noarch	—	Vendor Fix fix Workaround

Threats

Impact Important

References

13 references

URL	Category
https://access.redhat.com/errata/RHSA-2026:68786	self
https://access.redhat.com/security/updates/classi…	external
https://bugzilla.redhat.com/show_bug.cgi?id=2527155	external
https://security.access.redhat.com/data/csaf/v2/a…	self
https://access.redhat.com/security/cve/CVE-2026-81928	self
https://bugzilla.redhat.com/show_bug.cgi?id=2527155	external
https://www.cve.org/CVERecord?id=CVE-2026-81928	external
https://nvd.nist.gov/vuln/detail/CVE-2026-81928	external
https://datatracker.ietf.org/doc/html/rfc8945#sec…	external
https://metacpan.org/release/NLNETLABS/Net-DNS-1.…	external
https://metacpan.org/release/NLNETLABS/Net-DNS-1.…	external
https://metacpan.org/release/NLNETLABS/Net-DNS-1.…	external
https://rt.cpan.org/Ticket/Display.html?id=181125	external

JSON

To clipboard

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        "id": "CWE-835",
        "name": "Loop with Unreachable Exit Condition (\u0027Infinite Loop\u0027)"
      },
      "discovery_date": "2026-09-01T23:30:58.537256+00:00",
      "ids": [
        {
          "system_name": "Red Hat Bugzilla ID",
          "text": "2527155"
        }
      ],
      "notes": [
        {
          "category": "description",
          "text": "A flaw was found in Net::DNS versions before 1.57 for Perl. An attacker can cause a denial of service (DoS) by sending a specially crafted DNS message with a misplaced Transaction Signature (TSIG) record. When a system using Net::DNS, such as a forwarder or proxy, attempts to re-encode this message, it can lead to unbounded recursion and memory exhaustion, ultimately terminating the process. This vulnerability arises because the `sig_data` function fails to properly remove TSIG records from all sections of a DNS message, violating RFC 8945 section 5.2 requirements.",
          "title": "Vulnerability description"
        },
        {
          "category": "summary",
          "text": "perl-Net-DNS: Net::DNS: Denial of Service via unbounded recursion with misplaced TSIG records",
          "title": "Vulnerability summary"
        },
        {
          "category": "general",
          "text": "The CVSS score(s) listed for this vulnerability do not reflect the associated product\u0027s status, and are included for informational purposes to better understand the severity of this vulnerability.",
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        }
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          "summary": "https://metacpan.org/release/NLNETLABS/Net-DNS-1.56/source/lib/Net/DNS/RR/TSIG.pm#L245-262",
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            "AppStream-9.8.0.Z.MAIN.EUS:perl-Net-DNS-0:1.29-6.el9_8.1.src",
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          "url": "https://access.redhat.com/errata/RHSA-2026:68786"
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        {
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          "details": "To mitigate this issue, restrict network access to DNS services utilizing `perl-Net-DNS` to trusted clients or internal networks only, thereby limiting exposure. If the DNS service is not required to act as a forwarder or proxy, disable this functionality to prevent the vulnerable code path from being exercised.",
          "product_ids": [
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            "CRB-9.8.0.Z.MAIN.EUS:perl-Net-DNS-Nameserver-0:1.29-6.el9_8.1.noarch"
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            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
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            "CRB-9.8.0.Z.MAIN.EUS:perl-Net-DNS-Nameserver-0:1.29-6.el9_8.1.noarch"
          ]
        }
      ],
      "threats": [
        {
          "category": "impact",
          "details": "Important"
        }
      ],
      "title": "perl-Net-DNS: Net::DNS: Denial of Service via unbounded recursion with misplaced TSIG records"
    }
  ]
}

CVE-2026-81928 (GCVE-0-2026-81928)

Vulnerability from cvelistv5 – Published: 2026-09-01 23:14 – Updated: 2026-09-02 19:24

Title

Net::DNS versions before 1.57 for Perl allow memory exhaustion via unbounded recursion in sig_data when re-encoding a message with a misplaced TSIG record

Summary

Net::DNS versions before 1.57 for Perl allow memory exhaustion via unbounded recursion in sig_data when re-encoding a message with a misplaced TSIG record. sig_data signs a message by re-encoding it, and removes TSIG records only from the additional section. A TSIG decoded into the answer or authority section survives that step and is signed again, so encoding re-enters sig_data with no termination condition. Decoding does not reject such a message: a TSIG that is not the last record on the wire raises "misplaced or corrupt TSIG", but the error is caught, reported as a warning, and the record is left in the packet. RFC 8945 section 5.2 requires the message to be dropped. The recursion is reached only when the decoded TSIG carries an empty MAC, since a MAC recovered from the wire short-circuits the signing step. It is reached only from code that re-encodes a message it decoded, such as a forwarder or a proxy. A decoded message that is never re-encoded is unaffected. Message direction does not matter: a query reaches the same path as a response. Each cycle re-encodes the whole message, so fewer than 100 bytes on the wire exhaust available memory and terminate the process.

Severity

7.5 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-02 19:23 UTC

CWE

CWE-674 - Uncontrolled Recursion

Assigner

CPANSec redhat root

References

6 references

URL	Tags
https://metacpan.org/release/NLNETLABS/Net-DNS-1.…
https://metacpan.org/release/NLNETLABS/Net-DNS-1.…
https://datatracker.ietf.org/doc/html/rfc8945#sec…
https://rt.cpan.org/Ticket/Display.html?id=181125	issue-tracking
https://metacpan.org/release/NLNETLABS/Net-DNS-1.…	release-notes
http://www.openwall.com/lists/oss-security/2026/09/02/1

Impacted products

1 product

Vendor	Product	Version
		Affected: 0 , < 1.57 (custom)

Credits

Naseeb Dangi and Xiang Li from AOSP Lab @ Nankai University

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "providerMetadata": {
          "dateUpdated": "2026-09-02T10:08:21.418Z",
          "orgId": "af854a3a-2127-422b-91ae-364da2661108",
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        },
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          {
            "url": "http://www.openwall.com/lists/oss-security/2026/09/02/1"
          }
        ],
        "title": "CVE Program Container"
      },
      {
        "metrics": [
          {
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              "baseScore": 7.5,
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              "version": "3.1"
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                "id": "CVE-2026-81928",
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                  },
                  {
                    "Automatable": "yes"
                  },
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                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-09-02T19:23:53.602465Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
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        ],
        "providerMetadata": {
          "dateUpdated": "2026-09-02T19:24:12.656Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
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        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "reporter",
          "value": "Naseeb Dangi and Xiang Li from AOSP Lab @ Nankai University"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Net::DNS versions before 1.57 for Perl allow memory exhaustion via unbounded recursion in sig_data when re-encoding a message with a misplaced TSIG record.\n\nsig_data signs a message by re-encoding it, and removes TSIG records only from the additional section. A TSIG decoded into the answer or authority section survives that step and is signed again, so encoding re-enters sig_data with no termination condition. Decoding does not reject such a message: a TSIG that is not the last record on the wire raises \"misplaced or corrupt TSIG\", but the error is caught, reported as a warning, and the record is left in the packet. RFC 8945 section 5.2 requires the message to be dropped.\n\nThe recursion is reached only when the decoded TSIG carries an empty MAC, since a MAC recovered from the wire short-circuits the signing step. It is reached only from code that re-encodes a message it decoded, such as a forwarder or a proxy. A decoded message that is never re-encoded is unaffected. Message direction does not matter: a query reaches the same path as a response.\n\nEach cycle re-encodes the whole message, so fewer than 100 bytes on the wire exhaust available memory and terminate the process."
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-674",
              "description": "CWE-674 Uncontrolled Recursion",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-01T23:14:52.133Z",
        "orgId": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
        "shortName": "CPANSec"
      },
      "references": [
        {
          "url": "https://metacpan.org/release/NLNETLABS/Net-DNS-1.56/source/lib/Net/DNS/RR/TSIG.pm#L245-262"
        },
        {
          "url": "https://metacpan.org/release/NLNETLABS/Net-DNS-1.56/source/lib/Net/DNS/RR/TSIG.pm#L62-73"
        },
        {
          "url": "https://datatracker.ietf.org/doc/html/rfc8945#section-5.2"
        },
        {
          "tags": [
            "issue-tracking"
          ],
          "url": "https://rt.cpan.org/Ticket/Display.html?id=181125"
        },
        {
          "tags": [
            "release-notes"
          ],
          "url": "https://metacpan.org/release/NLNETLABS/Net-DNS-1.57/changes"
        }
      ],
      "solutions": [
        {
          "lang": "en",
          "value": "Upgrade to Net-DNS 1.57 or later."
        }
      ],
      "source": {
        "discovery": "UNKNOWN"
      },
      "title": "Net::DNS versions before 1.57 for Perl allow memory exhaustion via unbounded recursion in sig_data when re-encoding a message with a misplaced TSIG record",
      "workarounds": [
        {
          "lang": "en",
          "value": "For deployments that are not able to upgrade to Net-DNS 1.57, reject a decoded message before re-encoding it if a TSIG record appears anywhere but the final position of the additional section."
        }
      ],
      "x_generator": {
        "engine": "cpansec-cna-tool 0.1"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
    "assignerShortName": "CPANSec",
    "cveId": "CVE-2026-81928",
    "datePublished": "2026-09-01T23:14:52.133Z",
    "dateReserved": "2026-08-27T18:31:50.335Z",
    "dateUpdated": "2026-09-02T19:24:12.656Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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.