CVE-2026-50721

HIGHNVD 5.98.1▲
EchelonGraph scoreMEDIUM confidence

Score 8.1 from GitHub Security Advisory (severity: HIGH) published 2026-07-03. NVD baseline CVSS 5.9; sources differ by 2.2.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
8.1EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.4%CVSS: 5.9Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

Libreswan, via the function RSA_authenticate_hash_signature_raw_rsa(), did not correctly verify the length of the authentication hash when the SIG payload of an IKEv1 packet was encoded using PKCS #1 RSA Encryption as per RFC 2313. A remote attacker can use a variation on the Bleichenbacher attack to forge the SIG payload when small public exponents are being used (e.g., e=3), which could lead to impersonation. Additionally, a remote attacker, by encoding a shorter than expected hash in the SIG payload, could trigger an assertion leading to denial-of-service. The daemon aborts and restarts; continued exploitation causes sustained denial of service. Remote code execution is not possible. X.509 certificate verifications of remote IKE peers are not affected.

CVSS v3
5.9
EG Score
8.1HIGHmedium confidence
EG Risk
52
EG Risk 52/100

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%
Exploitation0% × 40%
Automatability100% × 15%
EPSS PROB
0.4%
EPSS %ILE
30th
KEV
Not listed

Published

July 2, 2026

Last Modified

July 9, 2026

Advisory Details (4)

Auto-updated Jul 3, 2026
Patch available.
generic

RFC 2313: PKCS #1: RSA Encryption Version 1.5 | RFC Editor

https://www.rfc-editor.org/rfc/rfc2313
generic
https://libreswan.org/security/CVE-2026-50722/CVE-2026-50722.txt
generic
https://libreswan.org/security/CVE-2026-50721/CVE-2026-50721.txt
generic

Index of /security/CVE-2026-50721/

https://libreswan.org/security/CVE-2026-50721/

Vendor Advisories for CVE-2026-50721(14)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(11)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
redhatrhcos-4.19.9.6.202609021231-02026-09-09redhat
redhatrhcos-4.21.9.6.202609021100-02026-09-08redhat
redhatrhcos-4.20.9.6.202609021029-02026-09-08redhat
redhatlibreswan-0:4.9-5.el9_2.52026-08-31redhat
redhatlibreswan-0:4.12-3.el9_4.22026-08-31redhat
redhatlibreswan-0:4.15-8.el9_6.12026-08-20redhat
redhatlibreswan-0:5.2-1.el10_0.52026-08-17redhat
redhatlibreswan-0:5.3.2-1.el10_22026-07-27redhat
redhatlibreswan-0:4.12-2.el8_10.62026-07-27redhat
redhatlibreswan-0:5.3.2-1.el9fdp2026-07-27redhat
redhatlibreswan-0:4.15-10.el9_82026-07-27redhat

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 rangeFix by version rangeDependents
libreswan4.10-1 ... 5.2-2.4 (27 versions)
  • every version on: no fix on record
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
libreswan4.10-2 ... 5.2-2.5 (18 versions)
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
libreswan5.2-2.2, 5.2-2.3, 5.2-2.4, 5.2-2.5
  • every version on: no fix on record
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
libreswan5.2-2.2, 5.2-2.3, 5.2-2.4
  • every version up to 5.2-2.5: fixed in 5.2-2.5
—

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 5× in last 7d / 41× 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 304 total refreshes for this CVE.

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

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

Frequently asked(5)

What is CVE-2026-50721?
CVE-2026-50721 is a high vulnerability published on July 2, 2026. Libreswan, via the function RSAauthenticatehashsignatureraw_rsa(), did not correctly verify the length of the authentication hash when the SIG payload of an IKEv1 packet was encoded using PKCS #1 RSA Encryption as per RFC 2313. A remote attacker can use a variation on the Bleichenbacher attack to…
When was CVE-2026-50721 disclosed?
CVE-2026-50721 was first published on July 2, 2026, with the most recent update on July 9, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-50721 actively exploited?
CVE-2026-50721 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.4% probability of exploitation in the next 30 days (30th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-50721?
CVE-2026-50721 has a CVSS v3 base score of 5.9 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 8.1 (HIGH).
How do I remediate CVE-2026-50721?
A fix for CVE-2026-50721 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-50721 are linked in the Vendor Advisories panel on this page.

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