CVE-2026-66746

MEDIUMPre-NVD 5.45.4—
EchelonGraph scoreHIGH 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%CVSS: 5.4Exploit: Elevated riskExposed: 0

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

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
5.4(high)
EG Risk
40(Track)
EG Risk 40/100SSVC: 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
Severity54% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
15%
KEV
Not listed

Published

July 28, 2026

Last Modified

July 30, 2026

Advisory Details (2)

Auto-updated Jul 28, 2026
🔬 Proof of concept available. No patch confirmed 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 rangeFixed inDependents
rust-rouille3.6.2+20250617+ds-1, 3.6.2+20250617+ds-2, 3.6.2+20250617+ds-3——

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 20× in last 7d / 84× 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. 2026-08-25 20:07 UTCEG score recompute
  2. 2026-08-25 20:07 UTCGHSA enrichment
  3. 2026-08-25 13:49 UTCEPSS rescore
  4. 2026-08-24 21:40 UTCEG score recompute
  5. 2026-08-24 21:40 UTCGHSA enrichment
  6. 2026-08-23 23:10 UTCGHSA enrichment
  7. 2026-08-23 00:48 UTCEG score recompute
  8. 2026-08-23 00:48 UTCGHSA enrichment
  9. 2026-08-23 00:19 UTCEPSS rescore
  10. 2026-08-22 02:26 UTCEG score recompute
  11. 2026-08-22 02:26 UTCGHSA enrichment
  12. 2026-08-21 23:49 UTCEPSS rescore
  13. 2026-08-21 04:03 UTCEG score recompute
  14. 2026-08-21 04:03 UTCGHSA enrichment
  15. 2026-08-20 22:56 UTCEPSS rescore
  16. 2026-08-20 05:39 UTCEG score recompute
  17. 2026-08-20 05:39 UTCGHSA enrichment
  18. 2026-08-19 17:04 UTCEPSS rescore
  19. 2026-08-19 07:16 UTCEG score recompute
  20. 2026-08-19 07:16 UTCGHSA enrichment
  21. 2026-08-18 13:48 UTCEPSS rescore
  22. 2026-08-18 08:47 UTCEG score recompute
  23. 2026-08-18 08:47 UTCGHSA enrichment
  24. 2026-08-17 13:47 UTCEPSS rescore
  25. 2026-08-17 10:10 UTCEG score recompute
Show 59 more
  1. 2026-08-17 10:10 UTCGHSA enrichment
  2. 2026-08-16 14:56 UTCEPSS rescore
  3. 2026-08-16 11:48 UTCEG score recompute
  4. 2026-08-16 11:48 UTCGHSA enrichment
  5. 2026-08-15 13:27 UTCEG score recompute
  6. 2026-08-15 13:27 UTCGHSA enrichment
  7. 2026-08-15 01:30 UTCEPSS rescore
  8. 2026-08-14 15:04 UTCEG score recompute
  9. 2026-08-14 15:04 UTCGHSA enrichment
  10. 2026-08-13 22:00 UTCEPSS rescore
  11. 2026-08-13 16:42 UTCGHSA enrichment
  12. 2026-08-12 18:19 UTCEG score recompute
  13. 2026-08-12 18:19 UTCGHSA enrichment
  14. 2026-08-12 13:51 UTCEPSS rescore
  15. 2026-08-11 19:49 UTCEG score recompute
  16. 2026-08-11 19:49 UTCGHSA enrichment
  17. 2026-08-11 00:00 UTCEPSS rescore
  18. 2026-08-10 21:27 UTCGHSA enrichment
  19. 2026-08-09 23:05 UTCEG score recompute
  20. 2026-08-09 23:05 UTCGHSA enrichment
  21. 2026-08-09 13:47 UTCEPSS rescore
  22. 2026-08-09 00:43 UTCEG score recompute
  23. 2026-08-09 00:43 UTCGHSA enrichment
  24. 2026-08-08 16:37 UTCEPSS rescore
  25. 2026-08-08 02:20 UTCEG score recompute
  26. 2026-08-08 02:20 UTCGHSA enrichment
  27. 2026-08-07 03:58 UTCGHSA enrichment
  28. 2026-08-06 05:36 UTCEG score recompute
  29. 2026-08-06 05:36 UTCGHSA enrichment
  30. 2026-08-05 19:17 UTCEPSS rescore
  31. 2026-08-05 19:17 UTCEPSS rescore
  32. 2026-08-05 07:15 UTCEG score recompute
  33. 2026-08-05 07:14 UTCGHSA enrichment
  34. 2026-08-04 15:10 UTCEPSS rescore
  35. 2026-08-04 10:39 UTCEPSS rescore
  36. 2026-08-04 08:50 UTCEG score recompute
  37. 2026-08-04 08:50 UTCGHSA enrichment
  38. 2026-08-03 10:36 UTCEPSS rescore
  39. 2026-08-03 10:28 UTCGHSA enrichment
  40. 2026-08-02 11:52 UTCEG score recompute
  41. 2026-08-02 11:52 UTCGHSA enrichment
  42. 2026-08-02 02:27 UTCEPSS rescore
  43. 2026-08-01 13:30 UTCEG score recompute
  44. 2026-08-01 13:30 UTCGHSA enrichment
  45. 2026-08-01 04:16 UTCEPSS rescore
  46. 2026-07-31 15:08 UTCGHSA enrichment
  47. 2026-07-30 16:45 UTCEG score recompute
  48. 2026-07-30 16:45 UTCGHSA enrichment
  49. 2026-07-30 16:28 UTCEPSS rescore
  50. 2026-07-30 12:43 UTCEG score recompute
  51. 2026-07-30 12:43 UTCGHSA enrichment
  52. 2026-07-30 01:30 UTCEPSS rescore
  53. 2026-07-29 14:20 UTCEG score recompute
  54. 2026-07-29 14:20 UTCGHSA enrichment
  55. 2026-07-29 13:59 UTCEG score recompute
  56. 2026-07-29 13:59 UTCGHSA enrichment
  57. 2026-07-28 16:40 UTCEG score recompute
  58. 2026-07-28 16:14 UTCEG score recompute
  59. 2026-07-28 16:13 UTCMITRE cvelistV5first tracked

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 in the National Vulnerability Database 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% probability of exploitation in the next 30 days, which ranks it in the top 85.0% of all scored CVEs.
What is the CVSS score of CVE-2026-66746?
CVE-2026-66746 has a CVSS v3 base score of 5.4 (NVD).
How do I remediate CVE-2026-66746?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-66746, 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

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-66746

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