CVE-2026-77640

MEDIUMNVD 5.35.3—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.3 under NVD CVSS v3. EPSS exploit probability: 0.2%, top 87% of all CVEs by exploit prediction. 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%CVSS: 5.3Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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
5.3(medium)
EG Risk
24(Track)
EG Risk 24/100SSVC: Track

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%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
13%
KEV
Not listed

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 rangeFixed inDependents
tor0.4.7.13-1 ... 0.4.9.9-1~bpo13+1 (46 versions)0.4.9.9-1—
Debian:13(1)
PackageVulnerable rangeFixed inDependents
tor0.4.8.16-1 ... 0.4.9.9-1~bpo13+1 (22 versions)0.4.9.11-0+deb13u1—
Debian:14(1)
PackageVulnerable rangeFixed inDependents
tor0.4.8.16-1 ... 0.4.9.9-1~bpo13+1 (19 versions)0.4.9.9-1—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 19× in last 7d / 66× 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.

  1. 2026-09-19 05:54 UTCEG score recompute
  2. 2026-09-19 05:54 UTCGHSA enrichment
  3. 2026-09-18 19:28 UTCEPSS rescore
  4. 2026-09-18 07:14 UTCEG score recompute
  5. 2026-09-18 07:14 UTCGHSA enrichment
  6. 2026-09-17 08:35 UTCEG score recompute
  7. 2026-09-17 08:34 UTCGHSA enrichment
  8. 2026-09-16 14:08 UTCEPSS rescore
  9. 2026-09-16 09:55 UTCEG score recompute
  10. 2026-09-16 09:55 UTCGHSA enrichment
  11. 2026-09-16 05:15 UTCEPSS rescore
  12. 2026-09-15 11:15 UTCEG score recompute
  13. 2026-09-15 11:15 UTCGHSA enrichment
  14. 2026-09-15 03:12 UTCEPSS rescore
  15. 2026-09-15 03:12 UTCEPSS rescore
  16. 2026-09-14 12:08 UTCEG score recompute
  17. 2026-09-14 12:08 UTCGHSA enrichment
  18. 2026-09-13 13:29 UTCEG score recompute
  19. 2026-09-13 13:29 UTCGHSA enrichment
  20. 2026-09-12 15:02 UTCEPSS rescore
  21. 2026-09-12 14:50 UTCGHSA enrichment
  22. 2026-09-11 16:11 UTCEG score recompute
  23. 2026-09-11 16:11 UTCGHSA enrichment
  24. 2026-09-11 14:53 UTCEPSS rescore
  25. 2026-09-10 17:23 UTCEG score recompute
Show 41 more
  1. 2026-09-10 17:23 UTCGHSA enrichment
  2. 2026-09-10 09:35 UTCEPSS rescore
  3. 2026-09-09 18:44 UTCEG score recompute
  4. 2026-09-09 18:44 UTCGHSA enrichment
  5. 2026-09-08 22:01 UTCEPSS rescore
  6. 2026-09-08 20:05 UTCEG score recompute▲ 1.60
  7. 2026-09-08 20:05 UTCGHSA enrichment
  8. 2026-09-08 18:29 UTCNVD updateCVSS v3 → 5.3 · severity → MEDIUM
  9. 2026-09-07 01:15 UTCEG score recompute
  10. 2026-09-07 01:15 UTCGHSA enrichment
  11. 2026-09-06 13:48 UTCEPSS rescore
  12. 2026-09-04 05:07 UTCEPSS rescore
  13. 2026-09-03 18:05 UTCEG score recompute
  14. 2026-09-03 18:05 UTCGHSA enrichment
  15. 2026-09-02 14:12 UTCEPSS rescore
  16. 2026-09-01 13:54 UTCEPSS rescore
  17. 2026-09-01 04:40 UTCEPSS rescore
  18. 2026-09-01 04:40 UTCEPSS rescore
  19. 2026-08-31 19:04 UTCEG score recompute
  20. 2026-08-31 19:03 UTCGHSA enrichment
  21. 2026-08-30 19:18 UTCEPSS rescore
  22. 2026-08-30 19:17 UTCEPSS rescore
  23. 2026-08-30 01:22 UTCEPSS rescore
  24. 2026-08-28 21:42 UTCEPSS rescore
  25. 2026-08-28 11:43 UTCEG score recompute
  26. 2026-08-28 11:43 UTCGHSA enrichment
  27. 2026-08-27 14:25 UTCEPSS rescore
  28. 2026-08-26 14:47 UTCEPSS rescore
  29. 2026-08-25 13:49 UTCEPSS rescore
  30. 2026-08-25 04:33 UTCEG score recompute
  31. 2026-08-25 04:33 UTCGHSA enrichment
  32. 2026-08-24 14:18 UTCEPSS rescore
  33. 2026-08-23 00:19 UTCEPSS rescore
  34. 2026-08-21 23:49 UTCEPSS rescore
  35. 2026-08-21 21:24 UTCEG score recompute
  36. 2026-08-21 21:24 UTCGHSA enrichment
  37. 2026-08-21 20:19 UTCEG score recompute
  38. 2026-08-21 20:19 UTCGHSA enrichment
  39. 2026-08-20 21:22 UTCEG score recompute
  40. 2026-08-20 21:07 UTCEG score recompute
  41. 2026-08-20 21:06 UTCMITRE cvelistV5first tracked

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 in the National Vulnerability Database 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% probability of exploitation in the next 30 days, which ranks it in the top 86.8% of all 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?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-77640, 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.

Dependency Blast Radius

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