CVE-2026-55203

CRITICALNVD 9.17.5▼
EchelonGraph scoreMEDIUM confidence

Score 7.5 from GitHub Security Advisory (severity: CRITICAL) published 2026-06-18. NVD baseline CVSS 9.1; sources differ by 1.6.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Trending — 4 sources updated this week
9.1
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 9.1Exploit: NoneExposed: 0

A fix is available — apply it.

HAProxy through 3.4.0, fixed in commit 5985276, contains an integer overflow vulnerability in the fcgi_conn structure's drl field that allows buffer misparse as new FCGI record headers. When contentLength is 65535 and paddingLength is 1 or more, the drl field wraps to 0, causing incorrect record consumption and allowing malicious FastCGI backends to desynchronize the FCGI framing parser, potentially causing request routing errors, response smuggling, or memory safety issues.

CVSS v3
9.1
EG Score
7.5(medium)
EPSS
24.0%
KEV
Not listed

Published

June 18, 2026

Last Modified

June 26, 2026

Advisory Details (2)

Auto-updated Jun 18, 2026
Upstream fix merged — awaiting tagged release. Sources: github_commit.
generic

HAProxy - Integer Overflow in FCGI Demux Record Length Field | Advisories | VulnCheck

https://www.vulncheck.com/advisories/haproxy-integer-overflow-in-fcgi-demux-record-length-field
github_commit

commit 598527673577 (haproxy/haproxy)

Fix landed in haproxy/haproxy commit 598527673577 — awaiting tagged release

https://github.com/haproxy/haproxy/commit/5985276735777634d8c85f1d73bb7764aab0d6dd

Vendor Advisories for CVE-2026-55203(2)

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

Patch Availability(1)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntuvim-haproxy (3.2.9-1ubuntu2.2) @ resolute2026-07-06ubuntu

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(1)

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

Additional Vendor Advisories

(1)

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 55× in last 7d / 127× 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 127 total refreshes for this CVE.

  1. 2026-07-06 22:30 UTCEG score recompute
  2. 2026-07-06 22:30 UTCVendor advisory
  3. 2026-07-06 22:30 UTCGHSA enrichment
  4. 2026-07-06 16:27 UTCEPSS rescore
  5. 2026-07-06 16:27 UTCEPSS rescore
  6. 2026-07-06 11:41 UTCEG score recompute
  7. 2026-07-06 11:41 UTCVendor advisory
  8. 2026-07-06 11:41 UTCGHSA enrichment
  9. 2026-07-06 02:23 UTCEPSS rescore
  10. 2026-07-06 02:23 UTCEPSS rescore
  11. 2026-07-05 23:54 UTCEG score recompute
  12. 2026-07-05 23:54 UTCVendor advisory
  13. 2026-07-05 23:54 UTCGHSA enrichment
  14. 2026-07-05 13:04 UTCEG score recompute
  15. 2026-07-05 13:04 UTCVendor advisory
  16. 2026-07-05 13:04 UTCGHSA enrichment
  17. 2026-07-05 02:31 UTCEPSS rescore
  18. 2026-07-05 02:30 UTCEPSS rescore
  19. 2026-07-05 02:15 UTCEG score recompute
  20. 2026-07-05 02:15 UTCVendor advisory
  21. 2026-07-05 02:15 UTCGHSA enrichment
  22. 2026-07-04 15:24 UTCEG score recompute
  23. 2026-07-04 15:24 UTCVendor advisory
  24. 2026-07-04 15:24 UTCGHSA enrichment
  25. 2026-07-04 06:31 UTCEPSS rescore
Show 75 more
  1. 2026-07-04 06:31 UTCEPSS rescore
  2. 2026-07-04 04:35 UTCEG score recompute
  3. 2026-07-04 04:35 UTCVendor advisory
  4. 2026-07-04 04:35 UTCGHSA enrichment
  5. 2026-07-03 16:49 UTCEG score recompute
  6. 2026-07-03 16:49 UTCVendor advisory
  7. 2026-07-03 16:49 UTCGHSA enrichment
  8. 2026-07-03 05:56 UTCEG score recompute
  9. 2026-07-03 05:56 UTCVendor advisory
  10. 2026-07-03 05:56 UTCGHSA enrichment
  11. 2026-07-02 19:06 UTCEG score recompute
  12. 2026-07-02 19:06 UTCVendor advisory
  13. 2026-07-02 19:05 UTCGHSA enrichment
  14. 2026-07-02 08:17 UTCEG score recompute
  15. 2026-07-02 08:17 UTCVendor advisory
  16. 2026-07-02 08:16 UTCGHSA enrichment
  17. 2026-07-01 21:27 UTCEG score recompute
  18. 2026-07-01 21:27 UTCVendor advisory
  19. 2026-07-01 21:27 UTCGHSA enrichment
  20. 2026-07-01 15:07 UTCEPSS rescore
  21. 2026-07-01 10:38 UTCEG score recompute
  22. 2026-07-01 10:38 UTCVendor advisory
  23. 2026-07-01 10:38 UTCGHSA enrichment
  24. 2026-06-30 23:49 UTCEG score recompute
  25. 2026-06-30 23:49 UTCVendor advisory
  26. 2026-06-30 23:49 UTCGHSA enrichment
  27. 2026-06-30 23:22 UTCEPSS rescore
  28. 2026-06-30 13:00 UTCEG score recompute
  29. 2026-06-30 13:00 UTCVendor advisory
  30. 2026-06-30 12:59 UTCGHSA enrichment
  31. 2026-06-30 02:10 UTCEG score recompute
  32. 2026-06-30 02:10 UTCVendor advisory
  33. 2026-06-30 02:10 UTCGHSA enrichment
  34. 2026-06-29 15:21 UTCEG score recompute
  35. 2026-06-29 15:21 UTCVendor advisory
  36. 2026-06-29 15:21 UTCGHSA enrichment
  37. 2026-06-29 14:06 UTCEPSS rescore
  38. 2026-06-29 14:06 UTCEPSS rescore
  39. 2026-06-29 04:23 UTCEG score recompute
  40. 2026-06-29 04:22 UTCGHSA enrichment
  41. 2026-06-28 17:32 UTCEG score recompute
  42. 2026-06-28 17:32 UTCVendor advisory
  43. 2026-06-28 17:32 UTCGHSA enrichment
  44. 2026-06-28 14:07 UTCEPSS rescore
  45. 2026-06-28 06:41 UTCEG score recompute
  46. 2026-06-28 06:41 UTCVendor advisory
  47. 2026-06-28 06:41 UTCGHSA enrichment
  48. 2026-06-28 04:56 UTCEPSS rescore
  49. 2026-06-28 04:56 UTCEPSS rescore
  50. 2026-06-27 19:52 UTCEG score recompute
  51. 2026-06-27 19:52 UTCVendor advisory
  52. 2026-06-27 19:52 UTCGHSA enrichment
  53. 2026-06-27 09:03 UTCEG score recompute
  54. 2026-06-27 09:03 UTCVendor advisory
  55. 2026-06-27 09:03 UTCGHSA enrichment
  56. 2026-06-27 03:08 UTCEPSS rescore
  57. 2026-06-26 22:14 UTCEG score recompute
  58. 2026-06-26 22:14 UTCVendor advisory
  59. 2026-06-26 22:14 UTCGHSA enrichment
  60. 2026-06-26 11:25 UTCEG score recompute
  61. 2026-06-26 11:25 UTCVendor advisory
  62. 2026-06-26 11:25 UTCGHSA enrichment
  63. 2026-06-26 03:53 UTCNVD updateCVSS v3 → 9.1 · severity → CRITICAL
  64. 2026-06-25 23:01 UTCEG score recompute
  65. 2026-06-25 23:01 UTCVendor advisory
  66. 2026-06-25 23:01 UTCGHSA enrichment
  67. 2026-06-25 13:49 UTCEPSS rescore
  68. 2026-06-25 12:11 UTCEG score recompute
  69. 2026-06-25 12:11 UTCGHSA enrichment
  70. 2026-06-25 01:22 UTCEG score recompute
  71. 2026-06-25 01:22 UTCGHSA enrichment
  72. 2026-06-24 14:33 UTCEG score recompute
  73. 2026-06-24 14:33 UTCGHSA enrichment
  74. 2026-06-24 14:05 UTCEPSS rescore
  75. 2026-06-24 03:44 UTCEG score recompute

Frequently asked(5)

What is CVE-2026-55203?
CVE-2026-55203 is a critical vulnerability published on June 18, 2026. HAProxy through 3.4.0, fixed in commit 5985276, contains an integer overflow vulnerability in the fcgi_conn structure's drl field that allows buffer misparse as new FCGI record headers. When contentLength is 65535 and paddingLength is 1 or more, the drl field wraps to 0, causing incorrect record…
When was CVE-2026-55203 disclosed?
CVE-2026-55203 was first published in the National Vulnerability Database on June 18, 2026, with the most recent update on June 26, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-55203 actively exploited?
CVE-2026-55203 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 24.0% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-55203?
CVE-2026-55203 has a CVSS v3 base score of 9.1 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 7.5.
How do I remediate CVE-2026-55203?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-55203, 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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