CVE-2026-27459

CRITICALNVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.8 under NVD CVSS v3. EPSS exploit probability: 0.7%, top 49% 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
9.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.9%CVSS: 9.8Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

pyOpenSSL is a Python wrapper around the OpenSSL library. Starting in version 22.0.0 and prior to version 26.0.0, if a user provided callback to set_cookie_generate_callback returned a cookie value greater than 256 bytes, pyOpenSSL would overflow an OpenSSL provided buffer. Starting in version 26.0.0, cookie values that are too long are now rejected.

CVSS v3
9.8
EG Score
9.8CRITICALmedium confidence
EG Risk
44
EG Risk 44/100

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
Severity98% × 45%
Exploitation1% × 40%
Automatability0% × 15%
EPSS PROB
0.9%
EPSS %ILE
57th
KEV
Not listed

Published

March 18, 2026

Last Modified

September 11, 2026

Advisory Details (10)

Auto-updated Oct 2, 2026
Patch available. Sources: github, github_commit.
github_commit

commit 57f09bb4bb05 (pyca/pyopenssl)

Fix landed in pyca/pyopenssl commit 57f09bb4bb05 — awaiting tagged release

https://github.com/pyca/pyopenssl/commit/57f09bb4bb051d3bc2a1abd36e9525313d5cd408
github Patch Available

Buffer overflow if DTLS cookie callback returned too long of a value · Advisory · pyca/pyopenssl · GitHub

https://github.com/pyca/pyopenssl/security/advisories/GHSA-5pwr-322w-8jr4
generic

pyopenssl/CHANGELOG.rst at 358cbf29c4e364c59930e53a270116249581eaa3 · pyca/pyopenssl · GitHub

https://github.com/pyca/pyopenssl/blob/358cbf29c4e364c59930e53a270116249581eaa3/CHANGELOG.rst
redhat Patch Available
https://access.redhat.com/errata/RHSA-2026:13545
redhat Patch Available
https://access.redhat.com/errata/RHSA-2026:13512
redhat Patch Available
https://access.redhat.com/errata/RHSA-2026:13508
redhat Patch Available
https://access.redhat.com/errata/RHSA-2026:11996
redhat Patch Available
https://access.redhat.com/errata/RHSA-2026:11916
redhat Patch Available
https://access.redhat.com/errata/RHSA-2026:11856
redhat Patch Available
https://access.redhat.com/errata/RHSA-2026:10754

Vendor Advisories for CVE-2026-27459(20)

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

Patch Availability(20)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
ubuntupython3-openssl (25.0.0-1ubuntu0.1) @ questing2026-09-10ubuntu
redhatansible-automation-platform-27/lightspeed-rhel9:17872175312026-08-24redhat
redhatjaeger-main-2.20.0-0.8.hum12026-07-30redhat
redhatquay/quay-rhel9:17849872732026-07-29redhat
redhatquay/quay-rhel8:17808913952026-06-09redhat
redhatquay/quay-rhel9:17799222052026-06-02redhat
redhatquay/quay-rhel8:17796893922026-05-26redhat
redhatquay/quay-rhel9:17792040862026-05-19redhat
redhatpython3.12-pyOpenSSL-0:26.0.0-2.el9pc2026-05-07redhat
redhatpython-pyOpenSSL-0:25.1.0-0.3.el9pc2026-05-07redhat
redhatpython-pyOpenSSL-0:24.1.0-2.el9pc2026-05-07redhat
redhatansible-automation-platform-26/platform-resource-runner-rhel9:17773903332026-05-04redhat
redhatansible-automation-platform-25/lightspeed-rhel8:17774038722026-05-04redhat
redhatpython3.12-pyOpenSSL-0:26.0.0-1.el9ap2026-05-04redhat
redhatquay/quay-rhel8:17767823692026-04-30redhat
redhatquay/quay-rhel8:17767526462026-04-29redhat
redhatquay/quay-rhel8:17767369102026-04-29redhat
redhatpython-pyOpenSSL-0:24.1.0-2.el8ui2026-04-27redhat
redhatrhtas/model-transparency-rhel9:17758154072026-04-16redhat
redhatpyopenssl-main-26.0.0-1.1.hum12026-04-09redhat

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:12(1)
PackageVulnerable rangeFix by version rangeDependents
pyopenssl23.0.0-1 ... 26.4.0-1 (22 versions)
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
pyopenssl25.0.0-1
  • every version up to 25.0.0-1+deb13u1: fixed in 25.0.0-1+deb13u1
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
pyopenssl25.0.0-1, 25.1.0-1, 25.1.0-2, 25.3.0-1, 25.3.0-2
  • every version up to 26.0.0-1: fixed in 26.0.0-1
—
PyPI(1)
PackageVulnerable rangeFix by version rangeDependents
pyopenssl22.0.0 ... 25.3.0 (15 versions)
  • 22.0.0 up to 26.0.0: fixed in 26.0.0
—

Weakness Classification(1)

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

Additional Vendor Advisories

(3)

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 5× in last 7d / 32× 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 192 total refreshes for this CVE.

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

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

Frequently asked(5)

What is CVE-2026-27459?
CVE-2026-27459 is a critical vulnerability published on March 18, 2026. pyOpenSSL is a Python wrapper around the OpenSSL library. Starting in version 22.0.0 and prior to version 26.0.0, if a user provided callback to setcookiegenerate_callback returned a cookie value greater than 256 bytes, pyOpenSSL would overflow an OpenSSL provided buffer. Starting in version…
When was CVE-2026-27459 disclosed?
CVE-2026-27459 was first published on March 18, 2026, with the most recent update on September 11, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-27459 actively exploited?
CVE-2026-27459 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.9% probability of exploitation in the next 30 days (57th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-27459?
CVE-2026-27459 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2026-27459?
A fix for CVE-2026-27459 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-27459 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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