CVE-2026-77640

MEDIUMNVD 5.35.3—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.3 under NVD CVSS v3. EPSS exploit probability: 0.4% (29th percentile of EPSS-scored CVEs). GitHub Security Advisory enrichment pending alignment with NVD CVSS.

Triggered by: NVD CVSS baseline
Sources: epss, ghsa, nvd
Trending — 3 sources updated this week
5.3EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.4%CVSS: 5.3Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

tor before 0.4.9.9 was prone to an infinite loop when decompressing a truncated zlib/gzip stream with done=1. A truncated stream never reaches Z_STREAM_END, causing zlib to return Z_BUF_ERROR with no input remaining, which buf_add_compress() mistook for a full output buffer and retried forever. Fixed by returning TOR_COMPRESS_ERROR in that case so the caller can abort cleanly. This is TROVE-2026-021.

CVSS v3
5.3
EG Score
5.3MEDIUMmedium confidence
EG Risk
24
EG Risk 24/100CISA SSVC

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
Severity53% × 45%
Exploitation0% × 40%
Automatability0% × 15%
CISA SSVC: Track at every mission impact level.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.4%
EPSS %ILE
29th
KEV
Not listed

CISA SSVCTrack at every mission impact level.

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

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

August 20, 2026

Last Modified

September 8, 2026

References (1)

Vendor Advisories for CVE-2026-77640(1)

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

Affected Packages

(3 across 3 ecosystems)
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
tor0.4.7.13-1 ... 0.4.9.9-1~bpo13+1 (46 versions)
  • every version up to 0.4.9.9-1: fixed in 0.4.9.9-1
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
tor0.4.8.16-1 ... 0.4.9.9-1~bpo13+1 (22 versions)
  • every version up to 0.4.9.11-0+deb13u1: fixed in 0.4.9.11-0+deb13u1
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
tor0.4.8.16-1 ... 0.4.9.9-1~bpo13+1 (19 versions)
  • every version up to 0.4.9.9-1: fixed in 0.4.9.9-1
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 18× in last 7d / 79× 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 109 total refreshes for this CVE.

  1. 2026-10-05 04:57 UTCEG score recompute
  2. 2026-10-05 04:57 UTCGHSA enrichment
  3. 2026-10-04 23:22 UTCEPSS rescore
  4. 2026-10-04 04:07 UTCEG score recompute
  5. 2026-10-04 04:07 UTCGHSA enrichment
  6. 2026-10-03 14:26 UTCEPSS rescore
  7. 2026-10-03 05:28 UTCEG score recompute
  8. 2026-10-03 05:28 UTCGHSA enrichment
  9. 2026-10-02 06:48 UTCEG score recompute
  10. 2026-10-02 06:48 UTCGHSA enrichment
  11. 2026-10-01 19:50 UTCEPSS rescore
  12. 2026-10-01 06:53 UTCEG score recompute
  13. 2026-10-01 06:53 UTCGHSA enrichment
  14. 2026-09-30 08:09 UTCEG score recompute
  15. 2026-09-30 08:09 UTCGHSA enrichment
  16. 2026-09-29 15:24 UTCEPSS rescore
  17. 2026-09-29 00:13 UTCEG score recompute
  18. 2026-09-29 00:13 UTCGHSA enrichment
  19. 2026-09-28 13:52 UTCEPSS rescore
  20. 2026-09-28 01:33 UTCEG score recompute
  21. 2026-09-28 01:33 UTCGHSA enrichment
  22. 2026-09-27 13:48 UTCEPSS rescore
  23. 2026-09-27 02:54 UTCEG score recompute
  24. 2026-09-27 02:54 UTCGHSA enrichment
  25. 2026-09-26 15:59 UTCEPSS rescore
Show 75 more
  1. 2026-09-26 00:28 UTCEPSS rescore
  2. 2026-09-25 00:40 UTCEG score recompute
  3. 2026-09-25 00:40 UTCGHSA enrichment
  4. 2026-09-24 14:04 UTCEPSS rescore
  5. 2026-09-23 23:28 UTCEG score recompute
  6. 2026-09-23 23:28 UTCGHSA enrichment
  7. 2026-09-23 17:54 UTCEPSS rescore
  8. 2026-09-23 00:36 UTCEG score recompute
  9. 2026-09-23 00:36 UTCGHSA enrichment
  10. 2026-09-22 16:01 UTCEPSS rescore
  11. 2026-09-22 01:57 UTCEG score recompute
  12. 2026-09-22 01:57 UTCGHSA enrichment
  13. 2026-09-21 21:09 UTCEPSS rescore
  14. 2026-09-21 03:18 UTCEG score recompute
  15. 2026-09-21 03:18 UTCGHSA enrichment
  16. 2026-09-20 20:16 UTCEPSS rescore
  17. 2026-09-20 04:33 UTCEG score recompute
  18. 2026-09-20 04:33 UTCGHSA enrichment
  19. 2026-09-19 05:54 UTCEG score recompute
  20. 2026-09-19 05:54 UTCGHSA enrichment
  21. 2026-09-18 19:28 UTCEPSS rescore
  22. 2026-09-18 07:14 UTCEG score recompute
  23. 2026-09-18 07:14 UTCGHSA enrichment
  24. 2026-09-17 08:35 UTCEG score recompute
  25. 2026-09-17 08:34 UTCGHSA enrichment
  26. 2026-09-16 14:08 UTCEPSS rescore
  27. 2026-09-16 09:55 UTCEG score recompute
  28. 2026-09-16 09:55 UTCGHSA enrichment
  29. 2026-09-16 05:15 UTCEPSS rescore
  30. 2026-09-15 11:15 UTCEG score recompute
  31. 2026-09-15 11:15 UTCGHSA enrichment
  32. 2026-09-15 03:12 UTCEPSS rescore
  33. 2026-09-15 03:12 UTCEPSS rescore
  34. 2026-09-14 12:08 UTCEG score recompute
  35. 2026-09-14 12:08 UTCGHSA enrichment
  36. 2026-09-13 13:29 UTCEG score recompute
  37. 2026-09-13 13:29 UTCGHSA enrichment
  38. 2026-09-12 15:02 UTCEPSS rescore
  39. 2026-09-12 14:50 UTCGHSA enrichment
  40. 2026-09-11 16:11 UTCEG score recompute
  41. 2026-09-11 16:11 UTCGHSA enrichment
  42. 2026-09-11 14:53 UTCEPSS rescore
  43. 2026-09-10 17:23 UTCEG score recompute
  44. 2026-09-10 17:23 UTCGHSA enrichment
  45. 2026-09-10 09:35 UTCEPSS rescore
  46. 2026-09-09 18:44 UTCEG score recompute
  47. 2026-09-09 18:44 UTCGHSA enrichment
  48. 2026-09-08 22:01 UTCEPSS rescore
  49. 2026-09-08 20:05 UTCEG score recompute▲ 1.60
  50. 2026-09-08 20:05 UTCGHSA enrichment
  51. 2026-09-08 18:29 UTCNVD updateCVSS v3 → 5.3 · severity → MEDIUM
  52. 2026-09-07 01:15 UTCEG score recompute
  53. 2026-09-07 01:15 UTCGHSA enrichment
  54. 2026-09-06 13:48 UTCEPSS rescore
  55. 2026-09-04 05:07 UTCEPSS rescore
  56. 2026-09-03 18:05 UTCEG score recompute
  57. 2026-09-03 18:05 UTCGHSA enrichment
  58. 2026-09-02 14:12 UTCEPSS rescore
  59. 2026-09-01 13:54 UTCEPSS rescore
  60. 2026-09-01 04:40 UTCEPSS rescore
  61. 2026-09-01 04:40 UTCEPSS rescore
  62. 2026-08-31 19:04 UTCEG score recompute
  63. 2026-08-31 19:03 UTCGHSA enrichment
  64. 2026-08-30 19:18 UTCEPSS rescore
  65. 2026-08-30 19:17 UTCEPSS rescore
  66. 2026-08-30 01:22 UTCEPSS rescore
  67. 2026-08-28 21:42 UTCEPSS rescore
  68. 2026-08-28 11:43 UTCEG score recompute
  69. 2026-08-28 11:43 UTCGHSA enrichment
  70. 2026-08-27 14:25 UTCEPSS rescore
  71. 2026-08-26 14:47 UTCEPSS rescore
  72. 2026-08-25 13:49 UTCEPSS rescore
  73. 2026-08-25 04:33 UTCEG score recompute
  74. 2026-08-25 04:33 UTCGHSA enrichment
  75. 2026-08-24 14:18 UTCEPSS rescore

Related CVEs(same product + same CWE)

Frequently asked(5)

What is CVE-2026-77640?
CVE-2026-77640 is a medium vulnerability published on August 20, 2026. tor before 0.4.9.9 was prone to an infinite loop when decompressing a truncated zlib/gzip stream with done=1. A truncated stream never reaches ZSTREAMEND, causing zlib to return ZBUFERROR with no input remaining, which bufaddcompress() mistook for a full output buffer and retried forever. Fixed by…
When was CVE-2026-77640 disclosed?
CVE-2026-77640 was first published on August 20, 2026, with the most recent update on September 8, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-77640 actively exploited?
CVE-2026-77640 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.4% probability of exploitation in the next 30 days (29th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-77640?
CVE-2026-77640 has a CVSS v3 base score of 5.3 (NVD).
How do I remediate CVE-2026-77640?
A fix for CVE-2026-77640 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-77640 are linked in the Vendor Advisories panel on this page.

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