CVE-2026-27459

CRITICALNVD 9.89.8
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to NVD's CVSS score.

This critical-severity CVE scores 9.8 under NVD CVSS v3. EPSS exploit probability: 0.8% (57th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from NVD CVSS v3
Sources: EPSS, NVD CVSS v3

Also known asEUVD-2026-12677 (ENISA EUVD) · GHSA-5pwr-322w-8jr4 (GitHub Security Advisories) · PYSEC-2026-2269 (OSV.dev)Source: ENISA EUVD

9.8EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines (the SSVC decision on this page).
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.8%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 impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity98% × 45%
Impact severity (EG Severity): CVSS 9.8 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.8% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Track* at high (mission-essential systems).
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.8%
EPSS %ILE
57th
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (9.8): severity, escalated by confirmed exploitation. This CVE's 9.8 is its impact severity (EG Severity), not escalated.

EG Severity
9.8 CRITICALCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.NVD CVSS v3 · CVSS v3.0 or v3.1
EG Likelihood
0.8% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-12). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at low or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

March 18, 2026

Last Modified

September 11, 2026

Advisory Details (10)

Auto-updated Nov 8, 2026
Patch available. Sources: github, github_commit.
Web page

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

https://github.com/pyca/pyopenssl/blob/358cbf29c4e364c59930e53a270116249581eaa3/CHANGELOG.rst
GitHub commit

commit 57f09bb4bb05 (pyca/pyopenssl)

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

https://github.com/pyca/pyopenssl/commit/57f09bb4bb051d3bc2a1abd36e9525313d5cd408
GitHub advisoryMentions a patch (unverified)

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
Red HatMentions a patch (unverified)
https://access.redhat.com/errata/RHSA-2026:13545
Red HatMentions a patch (unverified)
https://access.redhat.com/errata/RHSA-2026:13512
Red HatMentions a patch (unverified)
https://access.redhat.com/errata/RHSA-2026:13508
Red HatMentions a patch (unverified)
https://access.redhat.com/errata/RHSA-2026:11996
Red HatMentions a patch (unverified)
https://access.redhat.com/errata/RHSA-2026:11916
Red HatMentions a patch (unverified)
https://access.redhat.com/errata/RHSA-2026:11856
Red HatMentions a patch (unverified)
https://access.redhat.com/errata/RHSA-2026:10754

Patch Availability(24)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
ubuntupython3-openssl (25.0.0-1ubuntu0.1) @ questing2026-11-12ubuntu
redhatansible-automation-platform-26/ee-supported-rhel9:17919742202026-10-21redhat
redhatansible-automation-platform-27/ee-supported-rhel9:17923965182026-10-21redhat
redhatsatellite/iop-vmaas-rhel9:17896119982026-09-17redhat
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
redhatpython-pyOpenSSL-0:24.1.0-2.el9pc2026-05-07redhat
redhatpython-pyOpenSSL-0:25.1.0-0.3.el9pc2026-05-07redhat
redhatpython3.12-pyOpenSSL-0:26.0.0-2.el9pc2026-05-07redhat
redhatansible-automation-platform-25/lightspeed-rhel8:17774038722026-05-04redhat
redhatpython3.12-pyOpenSSL-0:26.0.0-1.el9ap2026-05-04redhat
redhatansible-automation-platform-26/platform-resource-runner-rhel9:17773903332026-05-04redhat
redhatquay/quay-rhel8:17767823692026-04-30redhat
redhatquay/quay-rhel8:17767369102026-04-29redhat
redhatquay/quay-rhel8:17767526462026-04-29redhat
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
pippyopenssl @ 26.0.0 (fixes >= 22.0.0, < 26.0.0)—ghsa

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

(6 across 6 ecosystems)
Alpine:v3.23(1)
PackageVulnerable rangeFix by version rangeDependents
py3-openssl—
  • every version up to 26.1.0-r0: fixed in 26.1.0-r0
—
Alpine:v3.24(1)
PackageVulnerable rangeFix by version rangeDependents
py3-openssl—
  • every version up to 26.1.0-r0: fixed in 26.1.0-r0
—
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

(5)

Data Freshness Timeline

(refreshed 21× in last 7d / 74× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed its CVE.org record (CNA or CISA ADP). An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). "EchelonGraph re-scored" is our own recompute of this CVE's score, not an update from a source, and is not counted in the refreshes above. Most recent first.

Showing the most recent 100 of 314 rows on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. None are among the latest 100 rows. The 214 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-11-12 23:40 UTCEchelonGraph re-scored
  2. 2026-11-12 23:40 UTCVendor advisory
  3. 2026-11-12 23:40 UTCGHSA enrichmentGHSA-5pwr-322w-8jr4 · GitHub severity HIGH
  4. 2026-11-12 16:33 UTCEPSS rescoreEPSS 0.8% · 57th percentile
  5. 2026-11-12 00:21 UTCEchelonGraph re-scored
  6. 2026-11-12 00:21 UTCVendor advisory
  7. 2026-11-12 00:21 UTCGHSA enrichmentGHSA-5pwr-322w-8jr4 · GitHub severity HIGH
  8. 2026-11-11 16:39 UTCEPSS rescoreEPSS 0.7% · 55th percentile
  9. 2026-11-11 01:02 UTCEchelonGraph re-scored
  10. 2026-11-11 01:02 UTCVendor advisory
  11. 2026-11-11 01:02 UTCGHSA enrichmentGHSA-5pwr-322w-8jr4 · GitHub severity HIGH
  12. 2026-11-10 16:43 UTCEPSS rescoreEPSS 0.7% · 55th percentile
  13. 2026-11-10 01:43 UTCEchelonGraph re-scored
  14. 2026-11-10 01:43 UTCVendor advisory
  15. 2026-11-10 01:43 UTCGHSA enrichmentGHSA-5pwr-322w-8jr4 · GitHub severity HIGH
  16. 2026-11-09 16:34 UTCEPSS rescoreEPSS 0.7% · 55th percentile
  17. 2026-11-09 02:24 UTCEchelonGraph re-scored
  18. 2026-11-09 02:24 UTCVendor advisory
  19. 2026-11-09 02:24 UTCGHSA enrichmentGHSA-5pwr-322w-8jr4 · GitHub severity HIGH
  20. 2026-11-08 16:38 UTCEPSS rescoreEPSS 0.7% · 55th percentile
  21. 2026-11-08 03:05 UTCEchelonGraph re-scored
  22. 2026-11-08 03:05 UTCVendor advisory
  23. 2026-11-08 03:05 UTCGHSA enrichmentGHSA-5pwr-322w-8jr4 · GitHub severity HIGH
  24. 2026-11-07 16:38 UTCEPSS rescoreEPSS 0.7% · 55th percentile
  25. 2026-11-07 03:46 UTCEchelonGraph re-scored
Show 75 more
  1. 2026-11-07 03:46 UTCVendor advisory
  2. 2026-11-07 03:46 UTCGHSA enrichmentGHSA-5pwr-322w-8jr4 · GitHub severity HIGH
  3. 2026-11-06 16:37 UTCEPSS rescoreEPSS 0.7% · 55th percentile
  4. 2026-11-06 04:28 UTCEchelonGraph re-scored
  5. 2026-11-06 04:28 UTCVendor advisory
  6. 2026-11-06 04:28 UTCGHSA enrichmentGHSA-5pwr-322w-8jr4 · GitHub severity HIGH
  7. 2026-11-06 04:25 UTCOSV refresh
  8. 2026-11-05 16:37 UTCEPSS rescoreEPSS 0.7% · 55th percentile
  9. 2026-11-05 05:10 UTCEchelonGraph re-scored
  10. 2026-11-05 05:10 UTCVendor advisory
  11. 2026-11-05 05:10 UTCGHSA enrichmentGHSA-5pwr-322w-8jr4 · GitHub severity HIGH
  12. 2026-11-04 16:35 UTCEPSS rescoreEPSS 0.7% · 54th percentile
  13. 2026-11-04 05:51 UTCEchelonGraph re-scored
  14. 2026-11-04 05:51 UTCVendor advisory
  15. 2026-11-04 05:51 UTCGHSA enrichmentGHSA-5pwr-322w-8jr4 · GitHub severity HIGH
  16. 2026-11-03 16:47 UTCEPSS rescoreEPSS 0.7% · 54th percentile
  17. 2026-11-03 06:32 UTCEchelonGraph re-scored
  18. 2026-11-03 06:32 UTCVendor advisory
  19. 2026-11-03 06:32 UTCGHSA enrichmentGHSA-5pwr-322w-8jr4 · GitHub severity HIGH
  20. 2026-11-02 16:44 UTCEPSS rescoreEPSS 0.7% · 54th percentile
  21. 2026-11-02 07:11 UTCEchelonGraph re-scored
  22. 2026-11-02 07:11 UTCVendor advisory
  23. 2026-11-02 07:11 UTCGHSA enrichmentGHSA-5pwr-322w-8jr4 · GitHub severity HIGH
  24. 2026-11-01 16:34 UTCEPSS rescoreEPSS 0.7% · 54th percentile
  25. 2026-11-01 07:52 UTCEchelonGraph re-scored
  26. 2026-11-01 07:52 UTCVendor advisory
  27. 2026-11-01 07:52 UTCGHSA enrichmentGHSA-5pwr-322w-8jr4 · GitHub severity HIGH
  28. 2026-10-31 16:32 UTCEPSS rescoreEPSS 0.7% · 54th percentile
  29. 2026-10-31 08:32 UTCEchelonGraph re-scored
  30. 2026-10-31 08:32 UTCVendor advisory
  31. 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.7% · 54th percentile
  32. 2026-10-30 09:13 UTCEchelonGraph re-scored
  33. 2026-10-30 09:13 UTCVendor advisory
  34. 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.7% · 54th percentile
  35. 2026-10-29 09:55 UTCEchelonGraph re-scored
  36. 2026-10-29 09:55 UTCVendor advisory
  37. 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.7% · 54th percentile
  38. 2026-10-28 10:36 UTCEchelonGraph re-scored
  39. 2026-10-28 10:36 UTCVendor advisory
  40. 2026-10-27 16:31 UTCEPSS rescoreEPSS 0.7% · 54th percentile
  41. 2026-10-27 10:25 UTCEchelonGraph re-scored
  42. 2026-10-27 10:25 UTCVendor advisory
  43. 2026-10-26 16:31 UTCEPSS rescoreEPSS 0.7% · 54th percentile
  44. 2026-10-26 11:06 UTCEchelonGraph re-scored
  45. 2026-10-26 11:06 UTCVendor advisory
  46. 2026-10-25 16:32 UTCEPSS rescoreEPSS 0.7% · 54th percentile
  47. 2026-10-25 14:38 UTCEchelonGraph re-scored
  48. 2026-10-25 11:48 UTCEchelonGraph re-scored
  49. 2026-10-25 11:48 UTCVendor advisory
  50. 2026-10-24 16:32 UTCEPSS rescoreEPSS 0.9% · 59th percentile
  51. 2026-10-24 12:29 UTCEchelonGraph re-scored
  52. 2026-10-24 12:29 UTCVendor advisory
  53. 2026-10-23 16:31 UTCEPSS rescoreEPSS 0.9% · 59th percentile
  54. 2026-10-23 13:07 UTCEchelonGraph re-scored
  55. 2026-10-23 13:07 UTCVendor advisory
  56. 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.9% · 59th percentile
  57. 2026-10-22 13:46 UTCEchelonGraph re-scored
  58. 2026-10-22 13:46 UTCVendor advisory
  59. 2026-10-21 16:32 UTCEPSS rescoreEPSS 0.9% · 59th percentile
  60. 2026-10-21 14:28 UTCEchelonGraph re-scored
  61. 2026-10-21 14:28 UTCVendor advisory
  62. 2026-10-20 16:32 UTCEPSS rescoreEPSS 0.9% · 59th percentile
  63. 2026-10-20 14:37 UTCEchelonGraph re-scored
  64. 2026-10-20 14:37 UTCVendor advisory
  65. 2026-10-19 16:31 UTCEPSS rescoreEPSS 0.9% · 59th percentile
  66. 2026-10-19 13:43 UTCEchelonGraph re-scored
  67. 2026-10-19 13:42 UTCVendor advisory
  68. 2026-10-18 16:31 UTCEPSS rescoreEPSS 0.9% · 59th percentile
  69. 2026-10-18 13:51 UTCVendor advisory
  70. 2026-10-18 03:51 UTCEchelonGraph re-scored
  71. 2026-10-17 16:33 UTCEPSS rescoreEPSS 0.9% · 59th percentile
  72. 2026-10-17 14:30 UTCEchelonGraph re-scored
  73. 2026-10-17 14:30 UTCVendor advisory
  74. 2026-10-16 16:41 UTCEPSS rescoreEPSS 0.9% · 59th percentile
  75. 2026-10-16 15:11 UTCEchelonGraph re-scored

Frequently asked(5)

What is CVE-2026-27459?
CVE-2026-27459 is a critical-severity vulnerability; its CVE record was 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 set_cookie_generate_callback returned a cookie value greater than 256 bytes, pyOpenSSL would overflow an OpenSSL provided buffer. Starting in version…
When was the CVE record for CVE-2026-27459 published?
The CVE record for CVE-2026-27459 was published on March 18, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of September 11, 2026; the record at its source may have been updated since.
Is CVE-2026-27459 actively exploited?
CVE-2026-27459 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.8% 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.

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