CVE-2021-33516

HIGHNVD 8.18.1—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.1 under NVD CVSS v3. EPSS exploit probability: 1.1% (63rd percentile of EPSS-scored CVEs). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
8.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1.1%CVSS: 8.1Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

An issue was discovered in GUPnP before 1.0.7 and 1.1.x and 1.2.x before 1.2.5. It allows DNS rebinding. A remote web server can exploit this vulnerability to trick a victim's browser into triggering actions against local UPnP services implemented using this library. Depending on the affected service, this could be used for data exfiltration, data tempering, etc.

CVSS v3
8.1
EG Score
8.1HIGHmedium confidence
EG Risk
41
EG Risk 41/100CISA 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
Severity81% × 45%
Exploitation1% × 40%
Automatability30% × 15%
CISA SSVC: Track at low or medium mission impact; Track or 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
1.1%
EPSS %ILE
64th
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Track or 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 (no KEV listing, exploit record or EPSS ≥ 50%) · Automatable unknown (not published for this CVE) · Technical impact partial (CVSS below 9.0). 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

May 24, 2021

Last Modified

November 21, 2024

Advisory Details (2)

Auto-updated Sep 16, 2026
Patch available.
generic

Security Issue: Server does not check value of Host header (#24) · Issues · GNOME / gupnp · GitLab

https://gitlab.gnome.org/GNOME/gupnp/-/issues/24
generic

Security-relevant releases for GUPnP issue CVE-2021-33516 - Development - GNOME Discourse

https://discourse.gnome.org/t/security-relevant-releases-for-gupnp-issue-cve-2021-33516/6536

Vendor Advisories for CVE-2021-33516(1)

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 / EcosystemFixed in / PatchReleasedSource
ubuntulibgupnp-1.2-0 (1.2.4-1ubuntu0.21.04.1) @ hirsute2026-05-26ubuntu
redhatgupnp-0:1.0.3-3.el8_12021-06-16redhat
redhatgupnp-0:1.0.2-6.el7_92021-06-14redhat
redhatgupnp-0:1.0.3-3.el8_22021-06-14redhat
redhatgupnp-0:1.0.6-2.el8_42021-06-09redhat

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

(4 across 4 ecosystems)
Debian:11(1)
PackageVulnerable rangeFixed inDependents
gupnp1.2.4-1 ... 1.6.9-4 (22 versions)——
Debian:12(1)
PackageVulnerable rangeFixed inDependents
gupnp—1.4.0-2—
Debian:13(1)
PackageVulnerable rangeFixed inDependents
gupnp—1.4.0-2—
Debian:14(1)
PackageVulnerable rangeFixed inDependents
gupnp—1.4.0-2—

Additional Vendor Advisories

(4)

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 6× in last 7d / 33× 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 184 total refreshes for this CVE.

  1. 2026-10-03 14:22 UTCEPSS rescore
  2. 2026-10-01 19:46 UTCEPSS rescore
  3. 2026-09-30 15:36 UTCEG score recompute
  4. 2026-09-30 15:00 UTCEPSS rescore
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  6. 2026-09-28 13:47 UTCEPSS rescore
  7. 2026-09-27 13:41 UTCEPSS rescore
  8. 2026-09-26 15:54 UTCEPSS rescore
  9. 2026-09-26 02:12 UTCOSV refresh
  10. 2026-09-26 00:21 UTCEPSS rescore
  11. 2026-09-24 14:00 UTCEPSS rescore
  12. 2026-09-23 13:44 UTCEPSS rescore
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  14. 2026-09-21 20:28 UTCEPSS rescore
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  24. 2026-09-13 16:43 UTCEPSS rescore
  25. 2026-09-12 14:57 UTCEPSS rescore
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  1. 2026-09-11 14:49 UTCEPSS rescore
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  3. 2026-09-08 21:56 UTCEPSS rescore
  4. 2026-09-07 15:58 UTCEPSS rescore
  5. 2026-09-06 17:01 UTCOSV refresh
  6. 2026-09-06 13:45 UTCEPSS rescore
  7. 2026-09-06 13:45 UTCEPSS rescore
  8. 2026-09-05 15:25 UTCEPSS rescore
  9. 2026-09-04 13:57 UTCEPSS rescore
  10. 2026-09-04 05:03 UTCEPSS rescore
  11. 2026-09-02 14:08 UTCEPSS rescore
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  14. 2026-08-30 19:14 UTCEPSS rescore
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  17. 2026-08-28 21:37 UTCEPSS rescore
  18. 2026-08-27 14:22 UTCEPSS rescore
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  20. 2026-08-25 13:46 UTCEPSS rescore
  21. 2026-08-24 14:13 UTCEPSS rescore
  22. 2026-08-23 00:16 UTCEPSS rescore
  23. 2026-08-21 23:46 UTCEPSS rescore
  24. 2026-08-20 22:52 UTCEPSS rescore
  25. 2026-08-20 03:04 UTCOSV refresh
  26. 2026-08-19 17:01 UTCEPSS rescore
  27. 2026-08-18 13:45 UTCEPSS rescore
  28. 2026-08-17 13:44 UTCEPSS rescore
  29. 2026-08-16 14:53 UTCEPSS rescore
  30. 2026-08-16 02:11 UTCEPSS rescore
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  32. 2026-08-15 01:27 UTCEPSS rescore
  33. 2026-08-13 21:57 UTCEPSS rescore
  34. 2026-08-12 13:48 UTCEPSS rescore
  35. 2026-08-11 13:38 UTCEPSS rescore
  36. 2026-08-09 13:44 UTCEPSS rescore
  37. 2026-08-08 16:33 UTCEPSS rescore
  38. 2026-08-07 16:24 UTCEPSS rescore
  39. 2026-08-06 13:43 UTCEPSS rescore
  40. 2026-08-05 19:14 UTCEPSS rescore
  41. 2026-08-04 21:57 UTCOSV refresh
  42. 2026-08-04 15:06 UTCEPSS rescore
  43. 2026-08-04 10:34 UTCEPSS rescore
  44. 2026-08-03 10:33 UTCEPSS rescore
  45. 2026-08-02 02:24 UTCEPSS rescore
  46. 2026-08-02 02:24 UTCEPSS rescore
  47. 2026-08-01 04:13 UTCEPSS rescore
  48. 2026-07-30 16:25 UTCEPSS rescore
  49. 2026-07-30 01:28 UTCEPSS rescore
  50. 2026-07-28 15:33 UTCEPSS rescore
  51. 2026-07-26 14:52 UTCEPSS rescore
  52. 2026-07-26 14:52 UTCEPSS rescore
  53. 2026-07-25 14:15 UTCEPSS rescore
  54. 2026-07-24 14:15 UTCEPSS rescore
  55. 2026-07-23 14:16 UTCEPSS rescore
  56. 2026-07-23 14:16 UTCEPSS rescore
  57. 2026-07-23 02:01 UTCEG score recompute
  58. 2026-07-22 22:48 UTCEG score recompute
  59. 2026-07-22 14:06 UTCEPSS rescore
  60. 2026-07-22 14:06 UTCEPSS rescore
  61. 2026-07-21 15:22 UTCEPSS rescore
  62. 2026-07-21 15:22 UTCEPSS rescore
  63. 2026-07-20 17:05 UTCEPSS rescore
  64. 2026-07-19 14:29 UTCEPSS rescore
  65. 2026-07-19 14:29 UTCEPSS rescore
  66. 2026-07-19 02:27 UTCEPSS rescore
  67. 2026-07-18 19:59 UTCOSV refresh
  68. 2026-07-18 10:02 UTCEPSS rescore
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  70. 2026-07-16 17:00 UTCEPSS rescore
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  72. 2026-07-15 16:55 UTCEPSS rescore
  73. 2026-07-15 01:58 UTCEPSS rescore
  74. 2026-07-13 22:27 UTCEPSS rescore
  75. 2026-07-12 05:44 UTCEPSS rescore

Related CVEs(same product)

Frequently asked(5)

What is CVE-2021-33516?
CVE-2021-33516 is a high vulnerability published on May 24, 2021. An issue was discovered in GUPnP before 1.0.7 and 1.1.x and 1.2.x before 1.2.5. It allows DNS rebinding. A remote web server can exploit this vulnerability to trick a victim's browser into triggering actions against local UPnP services implemented using this library. Depending on the affected…
When was CVE-2021-33516 disclosed?
CVE-2021-33516 was first published on May 24, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-33516 actively exploited?
CVE-2021-33516 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1.1% probability of exploitation in the next 30 days (64th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2021-33516?
CVE-2021-33516 has a CVSS v3 base score of 8.1 (NVD).
How do I remediate CVE-2021-33516?
A fix for CVE-2021-33516 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2021-33516 are linked in the Vendor Advisories panel on this page.

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