CVE-2021-26906

MEDIUMNVD 5.95.9—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.9 under NVD CVSS v3. EPSS exploit probability: 2.5%, top 17% of all CVEs by exploit prediction. 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
5.9EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 3%CVSS: 5.9Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

An issue was discovered in res_pjsip_session.c in Digium Asterisk through 13.38.1; 14.x, 15.x, and 16.x through 16.16.0; 17.x through 17.9.1; and 18.x through 18.2.0, and Certified Asterisk through 16.8-cert5. An SDP negotiation vulnerability in PJSIP allows a remote server to potentially crash Asterisk by sending specific SIP responses that cause an SDP negotiation failure.

CVSS v3
5.9
EG Score
5.9(medium)
EG Risk
32(Track)
EG Risk 32/100SSVC: Track

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
Severity59% × 45%
Exploitation3% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
3%
EPSS %ILE
84%
KEV
Not listed

Published

February 18, 2021

Last Modified

November 21, 2024

References (10)

Affected Packages

(15 across 15 ecosystems)
Alpine:v3.12(1)
PackageVulnerable rangeFixed inDependents
asterisk—16.16.1-r0—
Alpine:v3.13(1)
PackageVulnerable rangeFixed inDependents
asterisk—18.2.1-r0—
Alpine:v3.14(1)
PackageVulnerable rangeFixed inDependents
asterisk—18.2.1-r0—
Alpine:v3.15(1)
PackageVulnerable rangeFixed inDependents
asterisk—18.2.1-r0—
Alpine:v3.16(1)
PackageVulnerable rangeFixed inDependents
asterisk—18.2.1-r0—
Alpine:v3.17(1)
PackageVulnerable rangeFixed inDependents
asterisk—18.2.1-r0—
Alpine:v3.18(1)
PackageVulnerable rangeFixed inDependents
asterisk—18.2.1-r0—
Alpine:v3.19(1)
PackageVulnerable rangeFixed inDependents
asterisk—18.2.1-r0—
Alpine:v3.20(1)
PackageVulnerable rangeFixed inDependents
asterisk—18.2.1-r0—
Alpine:v3.21(1)
PackageVulnerable rangeFixed inDependents
asterisk—18.2.1-r0—
Alpine:v3.22(1)
PackageVulnerable rangeFixed inDependents
asterisk—18.2.1-r0—
Alpine:v3.23(1)
PackageVulnerable rangeFixed inDependents
asterisk—18.2.1-r0—
Alpine:v3.24(1)
PackageVulnerable rangeFixed inDependents
asterisk—18.2.1-r0—
Debian:11(1)
PackageVulnerable rangeFixed inDependents
asterisk—1:16.16.1~dfsg-1—
Debian:14(1)
PackageVulnerable rangeFixed inDependents
asterisk0.1.11-3 ... 1:16.2.1~dfsg-2 (237 versions)1:16.16.1~dfsg-1—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 8× in last 7d / 31× 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 163 total refreshes for this CVE.

  1. 2026-09-18 19:23 UTCEPSS rescore
  2. 2026-09-17 19:23 UTCEPSS rescore
  3. 2026-09-17 19:23 UTCEPSS rescore
  4. 2026-09-16 14:05 UTCEPSS rescore
  5. 2026-09-15 03:06 UTCEPSS rescore
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  7. 2026-09-13 16:43 UTCEPSS rescore
  8. 2026-09-12 14:57 UTCEPSS rescore
  9. 2026-09-11 14:49 UTCEPSS rescore
  10. 2026-09-11 09:33 UTCEPSS rescore
  11. 2026-09-08 21:56 UTCEPSS rescore
  12. 2026-09-07 15:58 UTCEPSS rescore
  13. 2026-09-06 21:43 UTCOSV refresh
  14. 2026-09-06 13:44 UTCEPSS rescore
  15. 2026-09-05 15:25 UTCEPSS rescore
  16. 2026-09-04 13:57 UTCEPSS rescore
  17. 2026-09-04 05:03 UTCEPSS rescore
  18. 2026-09-04 05:03 UTCEPSS rescore
  19. 2026-09-02 14:08 UTCEPSS rescore
  20. 2026-09-01 13:50 UTCEPSS rescore
  21. 2026-09-01 03:32 UTCEPSS rescore
  22. 2026-08-30 19:14 UTCEPSS rescore
  23. 2026-08-30 01:19 UTCEPSS rescore
  24. 2026-08-28 21:37 UTCEPSS rescore
  25. 2026-08-27 14:22 UTCEPSS rescore
Show 75 more
  1. 2026-08-26 14:42 UTCEPSS rescore
  2. 2026-08-25 13:45 UTCEPSS rescore
  3. 2026-08-24 14:12 UTCEPSS rescore
  4. 2026-08-23 00:16 UTCEPSS rescore
  5. 2026-08-21 23:46 UTCEPSS rescore
  6. 2026-08-20 22:52 UTCEPSS rescore
  7. 2026-08-20 07:55 UTCOSV refresh
  8. 2026-08-19 17:01 UTCEPSS rescore
  9. 2026-08-18 13:45 UTCEPSS rescore
  10. 2026-08-17 13:44 UTCEPSS rescore
  11. 2026-08-16 14:53 UTCEPSS rescore
  12. 2026-08-16 02:11 UTCEPSS rescore
  13. 2026-08-16 02:11 UTCEPSS rescore
  14. 2026-08-15 01:27 UTCEPSS rescore
  15. 2026-08-13 21:57 UTCEPSS rescore
  16. 2026-08-12 13:47 UTCEPSS rescore
  17. 2026-08-11 13:38 UTCEPSS rescore
  18. 2026-08-08 16:33 UTCEPSS rescore
  19. 2026-08-07 16:23 UTCEPSS rescore
  20. 2026-08-06 13:43 UTCEPSS rescore
  21. 2026-08-05 19:14 UTCEPSS rescore
  22. 2026-08-05 03:10 UTCOSV refresh
  23. 2026-08-04 15:06 UTCEPSS rescore
  24. 2026-08-04 10:34 UTCEPSS rescore
  25. 2026-08-03 10:33 UTCEPSS rescore
  26. 2026-08-02 02:24 UTCEPSS rescore
  27. 2026-08-01 04:13 UTCEPSS rescore
  28. 2026-07-30 16:25 UTCEPSS rescore
  29. 2026-07-30 16:25 UTCEPSS rescore
  30. 2026-07-30 01:28 UTCEPSS rescore
  31. 2026-07-30 01:27 UTCEPSS rescore
  32. 2026-07-28 15:33 UTCEPSS rescore
  33. 2026-07-26 14:52 UTCEPSS rescore
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  35. 2026-07-25 14:15 UTCEPSS rescore
  36. 2026-07-24 14:15 UTCEPSS rescore
  37. 2026-07-23 14:16 UTCEPSS rescore
  38. 2026-07-23 01:59 UTCEG score recompute
  39. 2026-07-22 22:45 UTCEG score recompute
  40. 2026-07-22 14:06 UTCEPSS rescore
  41. 2026-07-22 14:06 UTCEPSS rescore
  42. 2026-07-21 15:22 UTCEPSS rescore
  43. 2026-07-21 15:22 UTCEPSS rescore
  44. 2026-07-20 17:05 UTCEPSS rescore
  45. 2026-07-19 14:28 UTCEPSS rescore
  46. 2026-07-19 02:27 UTCEPSS rescore
  47. 2026-07-19 02:27 UTCEPSS rescore
  48. 2026-07-19 00:59 UTCOSV refresh
  49. 2026-07-18 10:02 UTCEPSS rescore
  50. 2026-07-18 10:02 UTCEPSS rescore
  51. 2026-07-16 17:00 UTCEPSS rescore
  52. 2026-07-15 16:55 UTCEPSS rescore
  53. 2026-07-15 16:55 UTCEPSS rescore
  54. 2026-07-15 01:58 UTCEPSS rescore
  55. 2026-07-13 22:27 UTCEPSS rescore
  56. 2026-07-13 22:27 UTCEPSS rescore
  57. 2026-07-13 06:10 UTCEPSS rescore
  58. 2026-07-12 05:44 UTCEPSS rescore
  59. 2026-07-12 05:44 UTCEPSS rescore
  60. 2026-07-11 08:25 UTCEPSS rescore
  61. 2026-07-11 08:25 UTCEPSS rescore
  62. 2026-07-09 19:07 UTCEPSS rescore
  63. 2026-07-08 15:12 UTCEPSS rescore
  64. 2026-07-07 13:43 UTCEPSS rescore
  65. 2026-07-06 16:25 UTCEPSS rescore
  66. 2026-07-06 16:25 UTCEPSS rescore
  67. 2026-07-06 02:21 UTCEPSS rescore
  68. 2026-07-06 02:21 UTCEPSS rescore
  69. 2026-07-05 02:28 UTCEPSS rescore
  70. 2026-07-04 06:29 UTCEPSS rescore
  71. 2026-07-04 06:29 UTCEPSS rescore
  72. 2026-07-02 16:57 UTCEPSS rescore
  73. 2026-07-01 15:03 UTCEPSS rescore
  74. 2026-07-01 08:18 UTCOSV refresh
  75. 2026-06-30 23:20 UTCEPSS rescore

Frequently asked(5)

What is CVE-2021-26906?
CVE-2021-26906 is a medium vulnerability published on February 18, 2021. An issue was discovered in respjsipsession.c in Digium Asterisk through 13.38.1; 14.x, 15.x, and 16.x through 16.16.0; 17.x through 17.9.1; and 18.x through 18.2.0, and Certified Asterisk through 16.8-cert5. An SDP negotiation vulnerability in PJSIP allows a remote server to potentially crash…
When was CVE-2021-26906 disclosed?
CVE-2021-26906 was first published in the National Vulnerability Database on February 18, 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-2021-26906 actively exploited?
CVE-2021-26906 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 3% probability of exploitation in the next 30 days, which ranks it in the top 15.7% of all scored CVEs.
What is the CVSS score of CVE-2021-26906?
CVE-2021-26906 has a CVSS v3 base score of 5.9 (NVD).
How do I remediate CVE-2021-26906?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-26906, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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