CVE-2026-81928: 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
Noroxi assessment
Priority: Monitor (action score 30/100)
- The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
- Probability of exploitation in the next 30 days: 0.68% (FIRST EPSS); higher than 52.5% of all records.
- Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
- According to CISA the attack is automatable: targets can be found by mass scanning.
- Fixed version: perl-Net-DNS (AlmaLinux:8) 1.15-2.el8_10; perl-Net-DNS (AlmaLinux:9) 1.29-6.el9_8.1; perl-Net-DNS-Nameserver (AlmaLinux:9) 1.29-6.el9_8.1.
Low priority for now. Upgrade to perl-Net-DNS (AlmaLinux:8) 1.15-2.el8_10; perl-Net-DNS (AlmaLinux:9) 1.29-6.el9_8.1; perl-Net-DNS-Nameserver (AlmaLinux:9) 1.29-6.el9_8.1 or later.
Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it
Primary sources: NVD · CVE.org · FIRST EPSS
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.
- Published
- Sep 1, 2026
- Updated
- Sep 3, 2026
- EPSS
- 0.6% · 52th percentile
- CWE
- CWE-674
Report tools
Action score
30
Monitor
Low priority for now.
- CVSS
- 30 / 40 · 7.5 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.6%
CISA SSVC decision
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
Get told when this record changes
- Not in KEV: no record of exploitation in the wild
- No public exploit code on record
- A fix has been released
If any of these changes, we'll tell you in the daily email digest.
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Noroxi analysis
What does it mean in your environment?
The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.
We use this product, ask for helpAffected systems
Is your version affected?
Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.
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Versions reported by the vendor
Affected version ranges reported by the assigning authority (CPANSec). Independent of NVD's CPE analysis and usually ahead of it.
cpan.org/modules Net-DNS
- before 1.57affected
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| AlmaLinux:8 | perl-Net-DNS | before 1.15-2.el8_10 | 1.15-2.el8_10 |
| AlmaLinux:9 | perl-Net-DNS | before 1.29-6.el9_8.1 | 1.29-6.el9_8.1 |
| AlmaLinux:9 | perl-Net-DNS-Nameserver | before 1.29-6.el9_8.1 | 1.29-6.el9_8.1 |
| Debian:12 | libnet-dns-perl | from 0 | — |
| Debian:14 | libnet-dns-perl | before 1.57-1 | 1.57-1 |
| openSUSE:Leap 16.0 | perl-Net-DNS | before 1.570.0-bp160.1.1 | 1.570.0-bp160.1.1 |
| openSUSE:Tumbleweed | perl-Net-DNS | before 1.570.0-1.1 | 1.570.0-1.1 |
| Red Hat:enterprise_linux:8::appstream | perl-Net-DNS | before 0:1.15-2.el8_10 | 0:1.15-2.el8_10 |
| Red Hat:enterprise_linux:9::appstream | perl-Net-DNS | before 0:1.29-6.el9_8.1 | 0:1.29-6.el9_8.1 |
| Red Hat:enterprise_linux:9::crb | perl-Net-DNS-Nameserver | before 0:1.29-6.el9_8.1 | 0:1.29-6.el9_8.1 |
| Rocky Linux:8 | perl-Net-DNS | before 0:1.15-2.el8_10 | 0:1.15-2.el8_10 |
| Rocky Linux:9 | perl-Net-DNS | before 0:1.29-6.el9_8.1 | 0:1.29-6.el9_8.1 |
| SUSE:Linux Enterprise Module for Basesystem 15 SP7 | perl-Net-DNS | before 1.14-150000.3.6.1 | 1.14-150000.3.6.1 |
| SUSE:Linux Enterprise Server LTSS Extended Security 12 SP5 | perl-Net-DNS | before 0.73-5.6.1 | 0.73-5.6.1 |
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| almalinux:perl-Net-DNS | 1.29-6.el9_8.1 · AlmaLinux:9 | Package registry (OSV) |
| almalinux:perl-Net-DNS-Nameserver | 1.29-6.el9_8.1 · AlmaLinux:9 | Package registry (OSV) |
| debian:libnet-dns-perl | 1.57-1 · Debian:14 | Package registry (OSV) |
| opensuse:perl-Net-DNS | 1.570.0-1.1 · openSUSE:Tumbleweed | Package registry (OSV) |
| red hat:perl-Net-DNS | 0:1.29-6.el9_8.1 · Red Hat:enterprise_linux:9::appstream | Package registry (OSV) |
| red hat:perl-Net-DNS-Nameserver | 0:1.29-6.el9_8.1 · Red Hat:enterprise_linux:9::crb | Package registry (OSV) |
| rocky linux:perl-Net-DNS | 0:1.29-6.el9_8.1 · Rocky Linux:9 | Package registry (OSV) |
| suse:perl-Net-DNS | 0.73-5.6.1 · SUSE:Linux Enterprise Server LTSS Extended Security 12 SP5 | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
- Naseeb Dangi and Xiang LiAOSP Lab @ Nankai Universityreporter
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- No account or password is required.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- none
- Integrity
- none
- Availability
- high · the service can be disrupted
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- None
- Integrity impact
- None
- Availability impact
- High
Weakness class (CWE)
CWE-674 · Uncontrolled RecursionCVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
nvd-secondary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Attack patterns (CAPEC)
ATT&CK techniques
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Change log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
Show all references (5 more)Show less
- metacpan.org/release/NLNETLABS/Net-DNS-1.56/source/lib/Net/DNS/RR/TSIG.pm#L245-262
- metacpan.org/release/NLNETLABS/Net-DNS-1.56/source/lib/Net/DNS/RR/TSIG.pm#L62-73
- metacpan.org/release/NLNETLABS/Net-DNS-1.57/changes
- rt.cpan.org/Ticket/Display.html?id=181125
- www.openwall.com/lists/oss-security/2026/09/02/1
Vendor advisories and official records. Exploit/PoC links are deliberately left out.