CVE-2026-55203

CRITICALNVD 9.19.1—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.1 under NVD CVSS v3. EPSS exploit probability: 0.3%, top 73% 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 — 4 sources updated this week
9.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 9.1Exploit: None knownExposed: 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
9.1(medium)
EG Risk
41(Track)
EG Risk 41/100SSVC: 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
Severity91% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
27%
KEV
Not listed

Published

June 18, 2026

Last Modified

July 14, 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(3)

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

Patch Availability(2)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntuvim-haproxy (3.2.9-1ubuntu2.2) @ resolute2026-07-28ubuntu
redhathaproxy-main-3.0.25-0.1.hum12026-07-03redhat

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 30× in last 7d / 142× 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 183 total refreshes for this CVE.

  1. 2026-07-29 01:44 UTCEG score recompute
  2. 2026-07-29 01:44 UTCVendor advisory
  3. 2026-07-29 01:44 UTCGHSA enrichment
  4. 2026-07-28 15:37 UTCEPSS rescore
  5. 2026-07-28 06:41 UTCVendor advisory
  6. 2026-07-28 06:41 UTCGHSA enrichment
  7. 2026-07-28 02:32 UTCVendor advisory
  8. 2026-07-28 02:32 UTCGHSA enrichment
  9. 2026-07-27 22:15 UTCVendor advisory
  10. 2026-07-27 22:15 UTCGHSA enrichment
  11. 2026-07-27 18:06 UTCEG score recompute
  12. 2026-07-27 18:06 UTCVendor advisory
  13. 2026-07-27 18:06 UTCGHSA enrichment
  14. 2026-07-27 11:09 UTCVendor advisory
  15. 2026-07-27 11:08 UTCGHSA enrichment
  16. 2026-07-27 07:00 UTCVendor advisory
  17. 2026-07-27 07:00 UTCGHSA enrichment
  18. 2026-07-27 01:39 UTCVendor advisory
  19. 2026-07-27 01:39 UTCGHSA enrichment
  20. 2026-07-26 21:30 UTCVendor advisory
  21. 2026-07-26 21:30 UTCGHSA enrichment
  22. 2026-07-26 17:20 UTCEG score recompute
  23. 2026-07-26 17:20 UTCVendor advisory
  24. 2026-07-26 17:20 UTCGHSA enrichment
  25. 2026-07-26 14:54 UTCEPSS rescore
Show 75 more
  1. 2026-07-25 14:18 UTCEPSS rescore
  2. 2026-07-24 14:18 UTCEPSS rescore
  3. 2026-07-23 14:18 UTCEPSS rescore
  4. 2026-07-23 03:20 UTCEG score recompute▲ 1.60
  5. 2026-07-22 14:08 UTCEPSS rescore
  6. 2026-07-20 17:08 UTCEPSS rescore
  7. 2026-07-19 14:31 UTCEPSS rescore
  8. 2026-07-19 14:31 UTCEPSS rescore
  9. 2026-07-19 02:29 UTCEPSS rescore
  10. 2026-07-18 10:04 UTCEPSS rescore
  11. 2026-07-16 23:23 UTCVendor advisory
  12. 2026-07-16 23:23 UTCGHSA enrichment
  13. 2026-07-16 17:03 UTCEPSS rescore
  14. 2026-07-16 12:33 UTCGHSA enrichment
  15. 2026-07-16 01:35 UTCVendor advisory
  16. 2026-07-16 01:35 UTCGHSA enrichment
  17. 2026-07-15 16:57 UTCEPSS rescore
  18. 2026-07-15 16:57 UTCEPSS rescore
  19. 2026-07-15 14:46 UTCVendor advisory
  20. 2026-07-15 14:46 UTCGHSA enrichment
  21. 2026-07-15 03:50 UTCVendor advisory
  22. 2026-07-15 03:50 UTCGHSA enrichment
  23. 2026-07-15 02:00 UTCEPSS rescore
  24. 2026-07-15 02:00 UTCEPSS rescore
  25. 2026-07-14 23:23 UTCNVD updateCVSS v3 → 9.1 · severity → CRITICAL
  26. 2026-07-14 21:35 UTCMITRE cvelistV5CVSS v3 → 7.5 · severity → HIGH
  27. 2026-07-14 17:00 UTCVendor advisory
  28. 2026-07-14 17:00 UTCGHSA enrichment
  29. 2026-07-14 06:10 UTCVendor advisory
  30. 2026-07-14 06:09 UTCGHSA enrichment
  31. 2026-07-13 22:31 UTCEPSS rescore
  32. 2026-07-13 19:14 UTCVendor advisory
  33. 2026-07-13 19:14 UTCGHSA enrichment
  34. 2026-07-13 08:25 UTCGHSA enrichment
  35. 2026-07-13 06:13 UTCEPSS rescore
  36. 2026-07-13 06:13 UTCEPSS rescore
  37. 2026-07-12 21:36 UTCVendor advisory
  38. 2026-07-12 21:35 UTCGHSA enrichment
  39. 2026-07-12 09:51 UTCVendor advisory
  40. 2026-07-12 09:51 UTCGHSA enrichment
  41. 2026-07-12 05:46 UTCEPSS rescore
  42. 2026-07-11 23:02 UTCVendor advisory
  43. 2026-07-11 23:01 UTCGHSA enrichment
  44. 2026-07-11 12:12 UTCVendor advisory
  45. 2026-07-11 12:12 UTCGHSA enrichment
  46. 2026-07-11 08:27 UTCEPSS rescore
  47. 2026-07-11 08:27 UTCEPSS rescore
  48. 2026-07-11 01:23 UTCVendor advisory
  49. 2026-07-11 01:22 UTCGHSA enrichment
  50. 2026-07-10 14:29 UTCVendor advisory
  51. 2026-07-10 14:29 UTCGHSA enrichment
  52. 2026-07-10 03:03 UTCVendor advisory
  53. 2026-07-10 03:02 UTCGHSA enrichment
  54. 2026-07-09 19:10 UTCEPSS rescore
  55. 2026-07-09 19:10 UTCEPSS rescore
  56. 2026-07-09 16:12 UTCVendor advisory
  57. 2026-07-09 16:11 UTCGHSA enrichment
  58. 2026-07-09 05:01 UTCVendor advisory
  59. 2026-07-09 05:01 UTCGHSA enrichment
  60. 2026-07-08 18:08 UTCVendor advisory
  61. 2026-07-08 18:08 UTCGHSA enrichment
  62. 2026-07-08 15:16 UTCEPSS rescore
  63. 2026-07-08 15:16 UTCEPSS rescore
  64. 2026-07-08 07:20 UTCVendor advisory
  65. 2026-07-08 07:20 UTCGHSA enrichment
  66. 2026-07-07 20:11 UTCVendor advisory
  67. 2026-07-07 20:11 UTCGHSA enrichment
  68. 2026-07-07 13:46 UTCEPSS rescore
  69. 2026-07-07 13:46 UTCEPSS rescore
  70. 2026-07-07 09:22 UTCVendor advisory
  71. 2026-07-07 09:21 UTCGHSA enrichment
  72. 2026-07-06 22:30 UTCVendor advisory
  73. 2026-07-06 22:30 UTCGHSA enrichment
  74. 2026-07-06 16:27 UTCEPSS rescore
  75. 2026-07-06 16:27 UTCEPSS rescore

Related CVEs(same vendor + same CWE)

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 July 14, 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 0% probability of exploitation in the next 30 days, which ranks it in the top 72.7% of all scored CVEs.
What is the CVSS score of CVE-2026-55203?
CVE-2026-55203 has a CVSS v3 base score of 9.1 (NVD).
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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