CVE-2026-66746

MEDIUMPre-NVD 5.45.4—
EchelonGraph scoreMEDIUM confidence

Score 5.4 from GitHub Security Advisory published 2026-07-28. A secondary CVSS source baseline 5.4; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 3 sources updated this weekElevated
5.4EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 5.4Exploit: Elevated riskExposed services: Not assessed

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

Rouille 0.4.0 through 3.6.2 contains an HTTP response splitting vulnerability that allows remote attackers to inject arbitrary response headers by embedding carriage return (0x0D) or line feed (0x0A) bytes into attacker-controlled input. Attackers can exploit percent-decoded query parameters reflected into response headers or inject bare LF characters into Cookie header values that are interpolated directly into Set-Cookie response headers, enabling cache poisoning, session fixation, and security header override attacks such as bypassing CSP or CORS policies.

CVSS v3
5.4
EG Score
5.4MEDIUMmedium confidence
EG Risk
40
EG Risk 40/100CISA 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
Severity54% × 45%
Exploitation40% × 40%
Automatability0% × 15%
CISA SSVC: Track at low or medium mission impact; Track* at high (mission-essential systems).
Action: No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines, and watch the vendor's advisory for the fix.
EPSS PROB
0.3%
EPSS %ILE
25th
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Track* at high (mission-essential systems).

No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines, and watch the vendor's advisory for the fix.

Exploitation public PoC (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

July 28, 2026

Last Modified

July 30, 2026

Advisory Details (2)

Auto-updated Jul 28, 2026
🔬 Proof of concept available. No fix on record yet.
generic

Rouille 0.4.0 - 3.6.2 HTTP Response Splitting via Header Injection | Advisories | VulnCheck

https://www.vulncheck.com/advisories/rouille-http-response-splitting-via-header-injection
generic🟡 PoC Available

GitHub - theopaid/HTTP-Response-Splitting-via-Unvalidated-Response-Header-Values-rouille-: Security Advisory: HTTP Response Splitting via Unvalidated Response Header Values (rouille) · GitHub

https://github.com/theopaid/HTTP-Response-Splitting-via-Unvalidated-Response-Header-Values-rouille-

Vendor Advisories for CVE-2026-66746(1)

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

Affected Packages

(1 across 1 ecosystem)
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
rust-rouille3.6.2+20250617+ds-1, 3.6.2+20250617+ds-2, 3.6.2+20250617+ds-3
  • every version on: no fix on record
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 10× in last 7d / 58× 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 176 total refreshes for this CVE.

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

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Frequently asked(5)

What is CVE-2026-66746?
CVE-2026-66746 is a medium vulnerability published on July 28, 2026. Rouille 0.4.0 through 3.6.2 contains an HTTP response splitting vulnerability that allows remote attackers to inject arbitrary response headers by embedding carriage return (0x0D) or line feed (0x0A) bytes into attacker-controlled input. Attackers can exploit percent-decoded query parameters…
When was CVE-2026-66746 disclosed?
CVE-2026-66746 was first published on July 28, 2026, with the most recent update on July 30, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-66746 actively exploited?
CVE-2026-66746 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (25th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-66746?
CVE-2026-66746 has a CVSS base score of 5.4 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-66746?
No fix for CVE-2026-66746 is confirmed yet. Until one is published, restrict network exposure of the affected system or apply the vendor's mitigation — for example, keep it off the internet or limit it to trusted networks — and watch the vendor's advisory for the fix. The vendor advisories EchelonGraph has for CVE-2026-66746 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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