CVE-2026-6100

HIGHPre-NVD 8.19.1▲
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.1 under the CNA's CVSS (NVD's own analysis pending). EPSS exploit probability: 0.1%, top 66% 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: cna:psf, epss
8.1
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 8.1Exploit: NoneExposed: 0

A fix is available — apply it.

Use-after-free (UAF) was possible in the lzma.LZMADecompressor, bz2.BZ2Decompressor, and gzip.GzipFile when a memory allocation fails with a MemoryError and the decompression instance is re-used. This scenario can be triggered if the process is under memory pressure. The fix cleans up the dangling pointer in this specific error condition.

The vulnerability is only present if the program re-uses decompressor instances across multiple decompression calls even after a MemoryError is raised during decompression. Using the helper functions to one-shot decompress data such as lzma.decompress(), bz2.decompress(), gzip.decompress(), and zlib.decompress() are not affected as a new decompressor instance is used per call. If the decompressor instance is not re-used after an error condition, this usage is similarly not vulnerable.

CVSS v3
8.1
EG Score
9.1(medium)
EPSS
43.7%
KEV
Not listed

Published

April 13, 2026

Last Modified

July 15, 2026

Advisory Details (9)

Auto-updated Jun 2, 2026
Upstream fix merged — awaiting tagged release. Sources: github_commit, github_pr.
generic

oss-security - [CVE-2026-6100] CPython: Use-after-free in lzma.LZMADecompressor, bz2.BZ2Decompressor, and gzip.GzipFile after re-use under memory pressure

http://www.openwall.com/lists/oss-security/2026/04/13/10
generic

Mailman 3 [CVE-2026-6100] Use-after-free in lzma.LZMADecompressor, bz2.BZ2Decompressor, and gzip.GzipFile after re-use under memory pressure - Security-announce - python.org

https://mail.python.org/archives/list/[email protected]/thread/HTWB2Z6KT5QQX4RYEZAFININDHNOSIF3/
github_pr

gh-148395: Fix a possible UAF in `{LZMA,BZ2,_Zlib}Decompressor`

Fix merged in python/cpython PR #148396 on 2026-04-13 — awaiting tagged release

https://github.com/python/cpython/pull/148396
generic

[CVE-2026-6100] Possible UAF in `{LZMA,BZ2,_Zlib}Decompressor` · Issue #148395 · python/cpython · GitHub

https://github.com/python/cpython/issues/148395
github_commit

commit e20c6c9667c9 (python/cpython)

Fix landed in python/cpython commit e20c6c9667c9 — awaiting tagged release

https://github.com/python/cpython/commit/e20c6c9667c99ecaab96e1a2b3767082841ffc8b
github_commit

commit c3cf71c3366f (python/cpython)

Fix landed in python/cpython commit c3cf71c3366f — awaiting tagged release

https://github.com/python/cpython/commit/c3cf71c3366fe49acb776a639405c0eea6169c20
github_commit

commit 8fc66aef6d7b (python/cpython)

Fix landed in python/cpython commit 8fc66aef6d7b — awaiting tagged release

https://github.com/python/cpython/commit/8fc66aef6d7b3ae58f43f5c66f9366cc8cbbfcd2
github_commit

commit 6a5f79c8d7bb (python/cpython)

Fix landed in python/cpython commit 6a5f79c8d7bb — awaiting tagged release

https://github.com/python/cpython/commit/6a5f79c8d7bbf22b083b240910c7a8781a59437d
github_commit

commit 47128e64f98c (python/cpython)

Fix landed in python/cpython commit 47128e64f98c — awaiting tagged release

https://github.com/python/cpython/commit/47128e64f98c3a20271138a98c2922bea2a3ee0e

Vendor Advisories for CVE-2026-6100(20)

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

Patch Availability(30)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatrhaiis/model-opt-cuda-rhel9:17806819842026-06-10redhat
redhatpython3.9-0:3.9.18-3.el9_4.132026-05-28redhat
redhatrhui5/rhua-rhel9:17797982222026-05-27redhat
redhatpython3-0:3.6.8-51.el8_8.152026-05-20redhat
redhatpython3.9-0:3.9.16-1.el9_2.142026-05-20redhat
redhatpython3.9-0:3.9.10-4.el9_0.112026-05-20redhat
redhatpython3-0:3.6.8-39.el8_4.112026-05-20redhat
redhatpython3.9-0:3.9.21-2.el9_6.62026-05-20redhat
redhatpython3.14-0:3.14.4-2.el10_22026-05-19redhat
redhatpython3.12-0:3.12.13-2.el10_22026-05-19redhat
redhatpython3.12-0:3.12.13-2.el9_82026-05-19redhat
redhatpython3.9-0:3.9.25-7.el9_82026-05-19redhat
redhatpython3.11-0:3.11.13-9.el9_82026-05-19redhat
redhatpython3.14-0:3.14.4-2.el9_82026-05-19redhat
redhatpython3.12-0:3.12.1-4.el9_4.132026-05-14redhat
redhatpython3-0:3.6.8-47.el8_6.132026-05-14redhat
redhatpython3.12-0:3.12.9-2.el10_0.92026-05-13redhat
redhatpython3.11-0:3.11.7-1.el9_4.132026-05-07redhat
redhatpython3.12-0:3.12.9-1.el9_6.82026-05-07redhat
redhatpython3.11-0:3.11.11-2.el9_6.72026-05-07redhat
redhatpython3.11-0:3.11.2-2.el9_2.122026-05-05redhat
redhatrhpam-7/rhpam-smartrouter-rhel8:7.13.5-4.17773257082026-05-05redhat
redhatrhui5/rhua-tp-rhel9:17774595042026-04-29redhat
redhatpython3.11-0:3.11.13-5.3.el9_72026-04-27redhat
redhatpython3.11-0:3.11.13-7.el8_102026-04-27redhat
redhatpython3.12-0:3.12.13-2.el8_102026-04-27redhat
redhatpython3-0:3.6.8-76.el8_102026-04-27redhat
redhatpython3.12-0:3.12.12-3.el10_1.32026-04-27redhat
redhatpython3.12-0:3.12.12-4.el9_7.32026-04-27redhat
redhatpython3.9-0:3.9.25-3.el9_7.32026-04-27redhat

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.

Weakness Classification(3)

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

Additional Vendor Advisories

(19)

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 11× in last 7d / 46× 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 166 total refreshes for this CVE.

  1. 2026-07-15 16:57 UTCEPSS rescore
  2. 2026-07-15 02:00 UTCEPSS rescore
  3. 2026-07-15 02:00 UTCEPSS rescore
  4. 2026-07-13 22:31 UTCEPSS rescore
  5. 2026-07-13 06:13 UTCEPSS rescore
  6. 2026-07-13 06:13 UTCEPSS rescore
  7. 2026-07-12 05:46 UTCEPSS rescore
  8. 2026-07-11 08:27 UTCEPSS rescore
  9. 2026-07-11 08:27 UTCEPSS rescore
  10. 2026-07-09 19:10 UTCEPSS rescore
  11. 2026-07-09 19:10 UTCEPSS rescore
  12. 2026-07-08 15:16 UTCEPSS rescore
  13. 2026-07-08 15:16 UTCEPSS rescore
  14. 2026-07-07 13:46 UTCEPSS rescore
  15. 2026-07-07 13:46 UTCEPSS rescore
  16. 2026-07-06 16:27 UTCEPSS rescore
  17. 2026-07-06 16:27 UTCEPSS rescore
  18. 2026-07-06 02:23 UTCEPSS rescore
  19. 2026-07-06 02:23 UTCEPSS rescore
  20. 2026-07-05 02:31 UTCEPSS rescore
  21. 2026-07-05 02:30 UTCEPSS rescore
  22. 2026-07-04 06:31 UTCEPSS rescore
  23. 2026-07-04 06:31 UTCEPSS rescore
  24. 2026-07-01 15:07 UTCEPSS rescore
  25. 2026-06-30 23:22 UTCEPSS rescore
Show 75 more
  1. 2026-06-30 04:32 UTCNVD updateCVSS v3 → 8.1 · severity → HIGH
  2. 2026-06-29 14:06 UTCEPSS rescore
  3. 2026-06-28 14:07 UTCEPSS rescore
  4. 2026-06-28 04:56 UTCEPSS rescore
  5. 2026-06-27 03:08 UTCEPSS rescore
  6. 2026-06-25 13:50 UTCEPSS rescore
  7. 2026-06-24 14:05 UTCEPSS rescore
  8. 2026-06-23 21:33 UTCEPSS rescore
  9. 2026-06-23 21:33 UTCEPSS rescore
  10. 2026-06-22 14:25 UTCEPSS rescore
  11. 2026-06-22 14:25 UTCEPSS rescore
  12. 2026-06-21 14:56 UTCEPSS rescore
  13. 2026-06-21 14:56 UTCEPSS rescore
  14. 2026-06-21 01:59 UTCEPSS rescore
  15. 2026-06-21 01:59 UTCEPSS rescore
  16. 2026-06-19 19:26 UTCEPSS rescore
  17. 2026-06-19 19:26 UTCEPSS rescore
  18. 2026-06-18 17:52 UTCEPSS rescore
  19. 2026-06-18 17:52 UTCEPSS rescore
  20. 2026-06-17 17:53 UTCEPSS rescore
  21. 2026-06-16 17:53 UTCEPSS rescore
  22. 2026-06-15 17:49 UTCEPSS rescore
  23. 2026-06-15 17:49 UTCEPSS rescore
  24. 2026-06-15 04:04 UTCEG score recompute
  25. 2026-06-15 04:04 UTCVendor advisory
  26. 2026-06-15 04:03 UTCGHSA enrichment
  27. 2026-06-14 23:18 UTCEPSS rescore
  28. 2026-06-14 21:43 UTCEG score recompute
  29. 2026-06-14 21:43 UTCVendor advisory
  30. 2026-06-14 21:43 UTCGHSA enrichment
  31. 2026-06-13 23:00 UTCEPSS rescore
  32. 2026-06-12 23:12 UTCEPSS rescore
  33. 2026-06-12 23:12 UTCEPSS rescore
  34. 2026-06-12 03:20 UTCEG score recompute
  35. 2026-06-12 03:20 UTCVendor advisory
  36. 2026-06-12 03:20 UTCGHSA enrichment
  37. 2026-06-11 23:27 UTCEG score recompute
  38. 2026-06-11 23:27 UTCVendor advisory
  39. 2026-06-11 23:27 UTCGHSA enrichment
  40. 2026-06-11 23:27 UTCGHSA enrichment
  41. 2026-06-11 19:36 UTCEG score recompute
  42. 2026-06-11 19:36 UTCVendor advisory
  43. 2026-06-11 19:36 UTCGHSA enrichment
  44. 2026-06-11 14:00 UTCEPSS rescore
  45. 2026-06-10 22:19 UTCEPSS rescore
  46. 2026-06-10 20:16 UTCEG score recompute
  47. 2026-06-10 20:16 UTCVendor advisory
  48. 2026-06-10 20:16 UTCGHSA enrichment
  49. 2026-06-10 16:25 UTCEG score recompute
  50. 2026-06-10 16:25 UTCVendor advisory
  51. 2026-06-10 16:25 UTCGHSA enrichment
  52. 2026-06-10 13:22 UTCEPSS rescore
  53. 2026-06-10 12:34 UTCEG score recompute
  54. 2026-06-10 12:34 UTCVendor advisory
  55. 2026-06-10 12:34 UTCGHSA enrichment
  56. 2026-06-10 08:43 UTCEG score recompute
  57. 2026-06-10 08:43 UTCVendor advisory
  58. 2026-06-10 08:43 UTCGHSA enrichment
  59. 2026-06-10 04:52 UTCEG score recompute
  60. 2026-06-10 04:52 UTCVendor advisory
  61. 2026-06-10 04:52 UTCGHSA enrichment
  62. 2026-06-10 00:44 UTCEG score recompute
  63. 2026-06-10 00:44 UTCVendor advisory
  64. 2026-06-10 00:44 UTCGHSA enrichment
  65. 2026-06-09 18:55 UTCEG score recompute
  66. 2026-06-09 18:55 UTCVendor advisory
  67. 2026-06-09 18:55 UTCGHSA enrichment
  68. 2026-06-09 15:04 UTCEG score recompute
  69. 2026-06-09 15:04 UTCVendor advisory
  70. 2026-06-09 15:04 UTCGHSA enrichment
  71. 2026-06-09 11:12 UTCEG score recompute
  72. 2026-06-09 11:12 UTCVendor advisory
  73. 2026-06-09 11:12 UTCGHSA enrichment
  74. 2026-06-08 14:27 UTCEG score recompute
  75. 2026-06-08 14:27 UTCVendor advisory

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-6100?
CVE-2026-6100 is a high vulnerability published on April 13, 2026. Use-after-free (UAF) was possible in the lzma.LZMADecompressor, bz2.BZ2Decompressor, and gzip.GzipFile when a memory allocation fails with a MemoryError and the decompression instance is re-used. This scenario can be triggered if the process is under memory pressure. The fix cleans up the dangling…
When was CVE-2026-6100 disclosed?
CVE-2026-6100 was first published in the National Vulnerability Database on April 13, 2026, with the most recent update on July 15, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-6100 actively exploited?
CVE-2026-6100 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 43.7% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-6100?
CVE-2026-6100 has a CVSS v3 base score of 8.1 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 9.1.
How do I remediate CVE-2026-6100?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-6100, 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.

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