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CVE-2026-55203

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.
Lifecycle PUBLISHED1 preserved revisionFact urn:baitaphish:canonical-cve-fact-revision:v2:e997f9fa064a1ed8bf569383e743678557f79d411be5ed5a426ca0772971ecf3
Known exploited
Not asserted
Disputed
No
Stale source
No
Conflicts
1

Preserved source conflicts

No provider value was silently selected as the winner.

cvss · 2 assertions

{"metric":{"Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","Safety":"NOT_DEFINED","attackComplexity":"LOW","attackRequirements":"PRESENT","attackVector":"NETWORK","baseScore":9,"baseSeverity":"CRITICAL","exploitMaturity":"NOT_DEFINED","privilegesRequired":"NONE","providerUrgency":"NOT_DEFINED","subAvailabilityImpact":"NONE","subConfidentialityImpact":"LOW","subIntegrityImpact":"HIGH","userInteraction":"NONE","valueDensity":"NOT_DEFINED","vectorString":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:L/SI:H/SA:N","version":"4.0","vulnAvailabilityImpact":"NONE","vulnConfidentialityImpac…

  • cve_program_cvelist_v5cvss
    urn:baitaphish:normalized-source-record:v2:ce7e0f156067395f19ae13db4581767f7f2b3ac21b39042d0f6094d2e8ef9c56 · sha256:63e22ca6a28d319b… · /containers/cna/metrics/0/cvssV4_0

{"metric":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":7.5,"baseSeverity":"HIGH","confidentialityImpact":"LOW","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"CHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:N","version":"3.1"},"metric_type":"cvssV3_1"}

  • cve_program_cvelist_v5cvss
    urn:baitaphish:normalized-source-record:v2:ce7e0f156067395f19ae13db4581767f7f2b3ac21b39042d0f6094d2e8ef9c56 · sha256:63e22ca6a28d319b… · /containers/cna/metrics/1/cvssV3_1

Affected products and versions

1 source assertion
{"defaultStatus":"unaffected","packageURL":"pkg:github/haproxy/haproxy","product":"haproxy","repo":"https://github.com/haproxy/haproxy","vendor":"haproxy","versions":[{"lessThanOrEqual":"3.4.0","status":"affected","version":"0","versionType":"semver"},{"status":"unaffected","version":"5985276735777634d8c85f1d73bb7764aab0d6dd","versionType":"git"}]}
  • cve_program_cvelist_v5affected
    urn:baitaphish:normalized-source-record:v2:ce7e0f156067395f19ae13db4581767f7f2b3ac21b39042d0f6094d2e8ef9c56 · sha256:63e22ca6a28d319b… · /containers/cna/affected/0

Provider-owned CVSS observations

2 source assertions
{"metric":{"Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","Safety":"NOT_DEFINED","attackComplexity":"LOW","attackRequirements":"PRESENT","attackVector":"NETWORK","baseScore":9,"baseSeverity":"CRITICAL","exploitMaturity":"NOT_DEFINED","privilegesRequired":"NONE","providerUrgency":"NOT_DEFINED","subAvailabilityImpact":"NONE","subConfidentialityImpact":"LOW","subIntegrityImpact":"HIGH","userInteraction":"NONE","valueDensity":"NOT_DEFINED","vectorString":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:L/SI:H/SA:N","version":"4.0","vulnAvailabilityImpact":"NONE","vulnConfidentialityImpac…
  • cve_program_cvelist_v5cvss
    urn:baitaphish:normalized-source-record:v2:ce7e0f156067395f19ae13db4581767f7f2b3ac21b39042d0f6094d2e8ef9c56 · sha256:63e22ca6a28d319b… · /containers/cna/metrics/0/cvssV4_0
{"metric":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":7.5,"baseSeverity":"HIGH","confidentialityImpact":"LOW","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"CHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:N","version":"3.1"},"metric_type":"cvssV3_1"}
  • cve_program_cvelist_v5cvss
    urn:baitaphish:normalized-source-record:v2:ce7e0f156067395f19ae13db4581767f7f2b3ac21b39042d0f6094d2e8ef9c56 · sha256:63e22ca6a28d319b… · /containers/cna/metrics/1/cvssV3_1

CWE assertions

1 source assertion
{"cweId":"CWE-190","description":"Integer Overflow or Wraparound","lang":"en","type":"CWE"}
  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:ce7e0f156067395f19ae13db4581767f7f2b3ac21b39042d0f6094d2e8ef9c56 · sha256:63e22ca6a28d319b… · /containers/cna/problemTypes/0/descriptions/0

Source references

2 source assertions
{"name":"Patch Commit","tags":["patch"],"url":"https://github.com/haproxy/haproxy/commit/5985276735777634d8c85f1d73bb7764aab0d6dd"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:ce7e0f156067395f19ae13db4581767f7f2b3ac21b39042d0f6094d2e8ef9c56 · sha256:63e22ca6a28d319b… · /containers/cna/references/0
{"tags":["third-party-advisory"],"url":"https://www.vulncheck.com/advisories/haproxy-integer-overflow-in-fcgi-demux-record-length-field"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:ce7e0f156067395f19ae13db4581767f7f2b3ac21b39042d0f6094d2e8ef9c56 · sha256:63e22ca6a28d319b… · /containers/cna/references/1

Attribution and limitations

  • CVE Program CVEList V5: Reproduce the MITRE copyright designation and CVE license in copies. Source →

Provider severity values are preserved separately. Baitaphish does not convert them into a risk rating, infer affected products, or treat EPSS as observed exploitation.

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