CVE-2026-55973

HIGHPre-NVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

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.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 4 sources updated this week
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.5%CVSS: 7.5Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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.

CVSS v3
7.5
EG Score
7.5HIGHmedium confidence
EG Risk
49
EG Risk 49/100CISA SSVC

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity75% × 45%
Exploitation0% × 40%
Automatability100% × 15%
CISA SSVC: Track at low or medium mission impact; Attend at high (mission-essential systems).
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
0.5%
EPSS %ILE
37th
KEV
Not listed

CISA SSVCTrack 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). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

July 22, 2026

Last Modified

July 24, 2026

Advisory Details (1)

Auto-updated Jul 22, 2026
Patch available.
generic
https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-55973.txt

Vendor 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.

Patch Availability(5)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
redhatrhcos-4.22.9.8.202609081748-02026-09-15redhat
redhatrhcos-4.22.9.8.202608251819-02026-09-01redhat
redhatunbound-0:1.24.2-3.el9_8.42026-08-17redhat
redhatunbound-0:1.24.2-7.el10_2.42026-08-17redhat
redhatunbound-main-1.25.2-0.1.hum12026-07-22redhat

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)
PackageVulnerable rangeFix by version rangeDependents
unbound—
  • 1.23.0 up to 1.25.2-r0: fixed in 1.25.2-r0
—
Alpine:v3.23(1)
PackageVulnerable rangeFix by version rangeDependents
unbound—
  • 1.23.0 up to 1.25.2-r0: fixed in 1.25.2-r0
—
Alpine:v3.24(1)
PackageVulnerable rangeFix by version rangeDependents
unbound—
  • 1.23.0 up to 1.25.2-r0: fixed in 1.25.2-r0
—
Debian:11(1)
PackageVulnerable rangeFix by version rangeDependents
unbound1.13.1-1 ... 1.25.2-1 (47 versions)
  • every version on: no fix on record
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
unbound1.17.1-2 ... 1.26.1-1 (26 versions)
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
unbound1.22.0-2 ... 1.26.0-2 (15 versions)
  • every version up to 1.26.1-0+deb13u1: fixed in 1.26.1-0+deb13u1
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
unbound1.22.0-2 ... 1.25.1-1 (9 versions)
  • every version up to 1.25.2-1: fixed in 1.25.2-1
—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 16× in last 7d / 87× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. 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. Most recent first.

Showing the most recent 100 of 309 total refreshes for this CVE.

  1. 2026-10-04 23:22 UTCEPSS rescore
  2. 2026-10-04 13:26 UTCEG score recompute
  3. 2026-10-04 13:26 UTCVendor advisory
  4. 2026-10-04 13:26 UTCGHSA enrichment
  5. 2026-10-03 14:26 UTCEPSS rescore
  6. 2026-10-03 03:34 UTCEG score recompute
  7. 2026-10-03 03:34 UTCVendor advisory
  8. 2026-10-03 03:34 UTCGHSA enrichment
  9. 2026-10-02 17:56 UTCEPSS rescore
  10. 2026-10-01 19:50 UTCEPSS rescore
  11. 2026-10-01 06:29 UTCEG score recompute
  12. 2026-10-01 06:29 UTCVendor advisory
  13. 2026-10-01 06:29 UTCGHSA enrichment
  14. 2026-09-30 15:03 UTCEPSS rescore
  15. 2026-09-29 15:22 UTCEPSS rescore
  16. 2026-09-28 13:51 UTCEPSS rescore
  17. 2026-09-28 05:18 UTCEG score recompute
  18. 2026-09-28 05:18 UTCVendor advisory
  19. 2026-09-28 05:18 UTCGHSA enrichment
  20. 2026-09-27 13:48 UTCEPSS rescore
  21. 2026-09-26 15:59 UTCEPSS rescore
  22. 2026-09-24 14:04 UTCEPSS rescore
  23. 2026-09-24 11:01 UTCVendor advisory
  24. 2026-09-24 11:01 UTCGHSA enrichment
  25. 2026-09-23 22:26 UTCEG score recompute
Show 75 more
  1. 2026-09-23 22:26 UTCVendor advisory
  2. 2026-09-23 22:26 UTCGHSA enrichment
  3. 2026-09-23 17:54 UTCEPSS rescore
  4. 2026-09-22 23:59 UTCEG score recompute
  5. 2026-09-22 23:59 UTCVendor advisory
  6. 2026-09-22 23:59 UTCGHSA enrichment
  7. 2026-09-20 20:16 UTCEPSS rescore
  8. 2026-09-20 02:04 UTCEG score recompute
  9. 2026-09-20 02:04 UTCVendor advisory
  10. 2026-09-20 02:04 UTCGHSA enrichment
  11. 2026-09-18 22:41 UTCEG score recompute
  12. 2026-09-18 22:41 UTCVendor advisory
  13. 2026-09-18 22:41 UTCGHSA enrichment
  14. 2026-09-18 19:28 UTCEPSS rescore
  15. 2026-09-18 03:11 UTCEG score recompute
  16. 2026-09-18 03:11 UTCVendor advisory
  17. 2026-09-18 03:11 UTCGHSA enrichment
  18. 2026-09-17 19:31 UTCEPSS rescore
  19. 2026-09-17 02:12 UTCEG score recompute
  20. 2026-09-17 02:12 UTCVendor advisory
  21. 2026-09-17 02:12 UTCGHSA enrichment
  22. 2026-09-16 14:08 UTCEPSS rescore
  23. 2026-09-16 07:04 UTCEG score recompute
  24. 2026-09-16 07:04 UTCVendor advisory
  25. 2026-09-16 07:04 UTCGHSA enrichment
  26. 2026-09-16 05:15 UTCEPSS rescore
  27. 2026-09-15 03:11 UTCEPSS rescore
  28. 2026-09-14 10:45 UTCVendor advisory
  29. 2026-09-14 10:45 UTCGHSA enrichment
  30. 2026-09-13 22:26 UTCEG score recompute
  31. 2026-09-13 22:26 UTCVendor advisory
  32. 2026-09-13 22:26 UTCGHSA enrichment
  33. 2026-09-13 16:47 UTCEPSS rescore
  34. 2026-09-13 07:16 UTCVendor advisory
  35. 2026-09-13 07:16 UTCGHSA enrichment
  36. 2026-09-12 18:58 UTCEG score recompute
  37. 2026-09-12 18:58 UTCVendor advisory
  38. 2026-09-12 18:58 UTCGHSA enrichment
  39. 2026-09-12 06:40 UTCVendor advisory
  40. 2026-09-12 06:40 UTCGHSA enrichment
  41. 2026-09-11 17:52 UTCEG score recompute
  42. 2026-09-11 17:52 UTCVendor advisory
  43. 2026-09-11 17:52 UTCGHSA enrichment
  44. 2026-09-11 14:53 UTCEPSS rescore
  45. 2026-09-10 21:38 UTCEG score recompute
  46. 2026-09-10 21:38 UTCVendor advisory
  47. 2026-09-10 21:38 UTCGHSA enrichment
  48. 2026-09-10 09:35 UTCEPSS rescore
  49. 2026-09-09 09:17 UTCEG score recompute
  50. 2026-09-09 09:17 UTCVendor advisory
  51. 2026-09-09 09:17 UTCGHSA enrichment
  52. 2026-09-08 22:01 UTCEPSS rescore
  53. 2026-09-07 21:42 UTCEG score recompute
  54. 2026-09-07 21:42 UTCVendor advisory
  55. 2026-09-07 21:42 UTCGHSA enrichment
  56. 2026-09-07 16:01 UTCEPSS rescore
  57. 2026-09-06 13:47 UTCEPSS rescore
  58. 2026-09-06 08:43 UTCVendor advisory
  59. 2026-09-06 08:43 UTCGHSA enrichment
  60. 2026-09-05 19:35 UTCEG score recompute
  61. 2026-09-05 19:35 UTCVendor advisory
  62. 2026-09-05 19:35 UTCGHSA enrichment
  63. 2026-09-05 07:15 UTCEG score recompute
  64. 2026-09-05 07:15 UTCVendor advisory
  65. 2026-09-05 07:15 UTCGHSA enrichment
  66. 2026-09-04 13:56 UTCEG score recompute
  67. 2026-09-04 13:56 UTCVendor advisory
  68. 2026-09-04 13:56 UTCGHSA enrichment
  69. 2026-09-04 05:07 UTCEPSS rescore
  70. 2026-09-02 14:12 UTCEPSS rescore
  71. 2026-09-01 23:41 UTCEG score recompute
  72. 2026-09-01 23:41 UTCVendor advisory
  73. 2026-09-01 23:41 UTCGHSA enrichment
  74. 2026-09-01 13:54 UTCEPSS rescore
  75. 2026-09-01 04:40 UTCEPSS rescore

Related CVEs(same product + same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-55973?
CVE-2026-55973 is a high vulnerability published on July 22, 2026. 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…
When was CVE-2026-55973 disclosed?
CVE-2026-55973 was first published on July 22, 2026, with the most recent update on July 24, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-55973 actively exploited?
CVE-2026-55973 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.5% probability of exploitation in the next 30 days (37th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-55973?
CVE-2026-55973 has a CVSS base score of 7.5 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-55973?
A fix for CVE-2026-55973 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-55973 are linked in the Vendor Advisories panel on this page.

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