In NLnet Labs Unbound 1.23.0 up to and including 1.25.1, when 'dns-error-reporting: yes' is set, the EDNS Report-Channel option (code 18) from the last upstream response is read and uses the option's length as the length of the agent domain. When a domain name check is performed on the agent domain, the returned lenght is not used and if the agent domain is followed by garbage, those bytes are moved onto the tail of the synthetic '_er.' report query name. That query name is later used in the iterator via a subquery to send out the DNS Error Report and when Unbound tries to walk that query name during 'find_closest_of_type()', it strips labels using the query name length rather than stopping at the embedded root, walks one byte past it, and feeds the first garbage byte to 'dname_query_hash()' as a label length writing over the stack variable 'labuf'. One ordinary upstream response from a delegated zone the attacker controls is sufficient to terminate the daemon.
CVE-2026-55973
“—” beside the score: it is equal to the CVSS score beside it.
Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2026-07-22. A secondary CVSS source baseline 7.5; sources differ by 0.0.
Also known asEUVD-2026-47681 (ENISA EUVD) · GHSA-g479-fg97-pf5w (GitHub Security Advisories)Source: ENISA EUVD
- High severity, but no confirmed exploitation yet
A fix is available — apply it.
- CVSS v3
- 7.5
- EG Score
- 7.5HIGHmedium confidence
- EG Risk
- 49EG Risk 49/100
EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.
How it’s computed (value × EchelonGraph’s weight)Severity75% × 45%Impact severity (EG Severity): CVSS 7.5 of 10. Never the KEV-floored or EPSS-lifted EG Score.Exploitation0.3% × 40%FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.Automatability100% × 15%CISA's SSVC Automatable value: yes (Vulnrichment).SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Attend at high (mission-essential systems).Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high. - EPSS PROB
- 0.3%
- EPSS %ILE
- 20th
- KEV
- Not listed
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (7.5): severity, escalated by confirmed exploitation. This CVE's 7.5 is its impact severity (EG Severity), not escalated.
- EG Severity
- 7.5 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 0.3% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-30). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at low or medium mission impact; Attend at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; 60 days if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Attend at high (mission-essential systems).
A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; 60 days if it is not.
The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it
Published
July 22, 2026
Last Modified
October 24, 2026
Advisory Details (1)
Auto-updated Jul 22, 2026Vendor Advisories for CVE-2026-55973(7)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
- RHSA-2026:66357Red Hat Product SecurityHigh
Red Hat Security Advisory: OpenShift Container Platform 4.22.14 bug fix and security update
- RHSA-2026:60440Red Hat Product SecurityHigh
Red Hat Security Advisory: OpenShift Container Platform 4.22.12 bug fix and security update
- RHSA-2026:55892Red Hat Product SecurityHigh
Red Hat Security Advisory: unbound security update
- RHSA-2026:55841Red Hat Product SecurityHigh
Red Hat Security Advisory: unbound security update
- CVE-2026-55973Microsoft Security Response Center (MSRC)Medium
'dns-error-reporting: yes' leads to stack buffer overflow
- GHSA-g479-fg97-pf5wGitHub Security AdvisoriesHigh
In NLnet Labs Unbound 1.23.0 up to and including 1.25.1, when 'dns-error-reporting: yes' is set,...
- RHSA-2026:43588Red Hat Product SecurityHigh
Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update
Patch Availability(6)
| Vendor / Ecosystem | Fix (by version range) / Patch | Released | Source |
|---|---|---|---|
| ubuntu | unbound-host (1.13.1-1ubuntu5.17) @ jammy | 2026-10-30 | ubuntu |
| redhat | openshift/ose-rhel-coreos-9:4.22.9.8.202609081748-0 | 2026-09-15 | redhat |
| redhat | openshift/ose-rhel-coreos-9:4.22.9.8.202608251819-0 | 2026-09-01 | redhat |
| redhat | unbound-0:1.24.2-3.el9_8.4 | 2026-08-17 | redhat |
| redhat | unbound-0:1.24.2-7.el10_2.4 | 2026-08-17 | redhat |
| redhat | unbound-main-1.25.2-0.1.hum1 | 2026-07-22 | redhat |
Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.
Affected Packages
(7 across 7 ecosystems)
Alpine:v3.22(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| unbound | — |
| — |
Alpine:v3.23(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| unbound | — |
| — |
Alpine:v3.24(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| unbound | — |
| — |
Debian:11(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| unbound | 1.13.1-1 ... 1.25.2-1 (47 versions) |
| — |
Debian:12(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| unbound | 1.17.1-2 ... 1.26.1-1 (26 versions) |
| — |
Debian:13(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| unbound | 1.22.0-2 ... 1.26.0-2 (15 versions) |
| — |
Debian:14(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| unbound | 1.22.0-2 ... 1.25.1-1 (9 versions) |
| — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Additional Vendor Advisories
(1)
Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.
Data Freshness Timeline
(refreshed 10× in last 7d / 51× in last 30d)
Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.
Showing the most recent 100 of 355 refreshes on record for this CVE.
A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. None are among the latest 100 rows. The 255 oldest rows on record are not shown and were not checked, so the counts can still include repeats.
- 2026-11-01 16:34 UTCEPSS rescoreEPSS 0.3% · 20th percentile
- 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.3% · 20th percentile
- 2026-10-30 22:20 UTCEG score recompute
- 2026-10-30 22:20 UTCVendor advisory
- 2026-10-30 22:20 UTCGHSA enrichmentGHSA-g479-fg97-pf5w · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.3% · 20th percentile
- 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.3% · 20th percentile
- 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.3% · 20th percentile
- 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.3% · 20th percentile
- 2026-10-26 16:31 UTCEPSS rescoreEPSS 0.3% · 20th percentile
- 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.3% · 20th percentile
- 2026-10-25 14:18 UTCEG score recompute
- 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.3% · 19th percentile
- 2026-10-24 13:32 UTCEG score recompute
- 2026-10-24 13:32 UTCVendor advisory
- 2026-10-24 13:32 UTCGHSA enrichmentGHSA-g479-fg97-pf5w · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.3% · 19th percentile
- 2026-10-23 11:52 UTCEG score recompute
- 2026-10-23 11:52 UTCVendor advisory
- 2026-10-23 11:52 UTCGHSA enrichmentGHSA-g479-fg97-pf5w · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.5% · 38th percentile
- 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.5% · 38th percentile
- 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.5% · 38th percentile
- 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.5% · 38th percentile
- 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.5% · 38th percentile
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- 2026-10-18 03:29 UTCEG score recompute
- 2026-10-17 16:34 UTCEPSS rescoreEPSS 0.5% · 38th percentile
- 2026-10-17 03:10 UTCEG score recompute
- 2026-10-17 03:10 UTCVendor advisory
- 2026-10-17 03:10 UTCGHSA enrichmentGHSA-g479-fg97-pf5w · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-10-16 16:42 UTCEPSS rescoreEPSS 0.5% · 38th percentile
- 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.5% · 38th percentile
- 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.5% · 38th percentile
- 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.5% · 38th percentile
- 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.5% · 38th percentile
- 2026-10-12 15:55 UTCEG score recompute
- 2026-10-11 19:38 UTCEG score recompute
- 2026-10-11 16:53 UTCEG score recompute
- 2026-10-11 14:16 UTCEG score recompute
- 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.5% · 38th percentile
- 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.5% · 37th percentile
- 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.5% · 37th percentile
- 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.5% · 37th percentile
- 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.5% · 37th percentile
- 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.5% · 37th percentile
- 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.5% · 37th percentile
- 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.5% · 37th percentile
- 2026-10-04 13:26 UTCEG score recompute
- 2026-10-04 13:26 UTCVendor advisory
- 2026-10-04 13:26 UTCGHSA enrichmentGHSA-g479-fg97-pf5w · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.5% · 37th percentile
- 2026-10-03 03:34 UTCEG score recompute
- 2026-10-03 03:34 UTCVendor advisory
- 2026-10-03 03:34 UTCGHSA enrichmentGHSA-g479-fg97-pf5w · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.5% · 37th percentile
- 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.5% · 37th percentile
- 2026-10-01 06:29 UTCEG score recompute
- 2026-10-01 06:29 UTCVendor advisory
- 2026-10-01 06:29 UTCGHSA enrichmentGHSA-g479-fg97-pf5w · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.5% · 37th percentile
- 2026-09-29 15:22 UTCEPSS rescoreEPSS 0.5% · 37th percentile
- 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.5% · 37th percentile
- 2026-09-28 05:18 UTCEG score recompute
- 2026-09-28 05:18 UTCVendor advisory
- 2026-09-28 05:18 UTCGHSA enrichmentGHSA-g479-fg97-pf5w · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.5% · 37th percentile
- 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.5% · 37th percentile
- 2026-09-24 14:04 UTCEPSS rescoreEPSS 0.5% · 37th percentile
- 2026-09-24 11:01 UTCVendor advisory
- 2026-09-24 11:01 UTCGHSA enrichmentGHSA-g479-fg97-pf5w · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-09-23 22:26 UTCEG score recompute
- 2026-09-23 22:26 UTCVendor advisory
- 2026-09-23 22:26 UTCGHSA enrichmentGHSA-g479-fg97-pf5w · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.3% · 20th percentile
- 2026-09-22 23:59 UTCEG score recompute
- 2026-09-22 23:59 UTCVendor advisory
- 2026-09-22 23:59 UTCGHSA enrichmentGHSA-g479-fg97-pf5w · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.3% · 20th percentile
- 2026-09-20 02:04 UTCEG score recompute
- 2026-09-20 02:04 UTCVendor advisory
- 2026-09-20 02:04 UTCGHSA enrichmentGHSA-g479-fg97-pf5w · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-09-18 22:41 UTCEG score recompute
- 2026-09-18 22:41 UTCVendor advisory
- 2026-09-18 22:41 UTCGHSA enrichmentGHSA-g479-fg97-pf5w · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.3% · 20th percentile
- 2026-09-18 03:11 UTCEG score recompute
- 2026-09-18 03:11 UTCVendor advisory
- 2026-09-18 03:11 UTCGHSA enrichmentGHSA-g479-fg97-pf5w · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-09-17 19:31 UTCEPSS rescoreEPSS 0.3% · 20th percentile
- 2026-09-17 02:12 UTCEG score recompute
- 2026-09-17 02:12 UTCVendor advisory
- 2026-09-17 02:12 UTCGHSA enrichmentGHSA-g479-fg97-pf5w · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.3% · 20th percentile
- 2026-09-16 07:04 UTCEG score recompute
- 2026-09-16 07:04 UTCVendor advisory
- 2026-09-16 07:04 UTCGHSA enrichmentGHSA-g479-fg97-pf5w · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.3% · 20th percentile
- 2026-09-15 03:11 UTCEPSS rescoreEPSS 0.3% · 20th percentile
- 2026-09-14 10:45 UTCVendor advisory
- 2026-09-14 10:45 UTCGHSA enrichmentGHSA-g479-fg97-pf5w · GitHub severity HIGH · GitHub CVSS 7.5
Related CVEs(same product + same vendor + same CWE)
Same product
10 shownAlpine:v3.22:unbound
Same vendor
10 shownredhat:RHSA-2026:43588 · redhat:RHSA-2026:60440 · ubuntu:USN-8946-1
Frequently asked(5)
What is CVE-2026-55973?
When was CVE-2026-55973 made public?
Is CVE-2026-55973 actively exploited?
What is the CVSS score of CVE-2026-55973?
How do I remediate CVE-2026-55973?
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-55973
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