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CVE-2026-58055

nghttp2's nghttpx proxy through 1.69.0 forwards an HTTP/1.1 Upgrade request that also carries a Content-Length header and body onto reusable keep-alive backend connections, re-adding the Upgrade and Connection headers while passing Content-Length verbatim. A backend that resolves the resulting ambiguous message in the attacker's favor enables HTTP request/response smuggling and cross-client response-queue poisoning.
Lifecycle PUBLISHED1 preserved revisionFact urn:baitaphish:canonical-cve-fact-revision:v2:eaaf8d620a32d730343f5256c7b3c29dc084183ba9253e10db77e5e8c86492bd
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":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":5.4,"baseSeverity":"MEDIUM","confidentialityImpact":"LOW","integrityImpact":"LOW","privilegesRequired":"NONE","scope":"CHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N","version":"3.1"},"metric_type":"cvssV3_1"}

  • cve_program_cvelist_v5cvss
    urn:baitaphish:normalized-source-record:v2:c759effd3c5dcdd57c65dfef784205ce91fa66e11e27d475f498db7f98a71b54 · sha256:1f281be267402e83… · /containers/cna/metrics/0/cvssV3_1

{"metric":{"attackComplexity":"HIGH","attackRequirements":"NONE","attackVector":"NETWORK","baseScore":6.3,"baseSeverity":"MEDIUM","privilegesRequired":"NONE","subAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"LOW","userInteraction":"NONE","vectorString":"CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:L/SA:N","version":"4.0","vulnAvailabilityImpact":"NONE","vulnConfidentialityImpact":"LOW","vulnIntegrityImpact":"LOW"},"metric_type":"cvssV4_0"}

  • cve_program_cvelist_v5cvss
    urn:baitaphish:normalized-source-record:v2:c759effd3c5dcdd57c65dfef784205ce91fa66e11e27d475f498db7f98a71b54 · sha256:1f281be267402e83… · /containers/cna/metrics/1/cvssV4_0

Affected products and versions

1 source assertion
{"defaultStatus":"affected","product":"nghttp2","vendor":"nghttp2","versions":[{"lessThanOrEqual":"1.69.0","status":"affected","version":"0","versionType":"semver"}]}
  • cve_program_cvelist_v5affected
    urn:baitaphish:normalized-source-record:v2:c759effd3c5dcdd57c65dfef784205ce91fa66e11e27d475f498db7f98a71b54 · sha256:1f281be267402e83… · /containers/cna/affected/0

Provider-owned CVSS observations

2 source assertions
{"metric":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":5.4,"baseSeverity":"MEDIUM","confidentialityImpact":"LOW","integrityImpact":"LOW","privilegesRequired":"NONE","scope":"CHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N","version":"3.1"},"metric_type":"cvssV3_1"}
  • cve_program_cvelist_v5cvss
    urn:baitaphish:normalized-source-record:v2:c759effd3c5dcdd57c65dfef784205ce91fa66e11e27d475f498db7f98a71b54 · sha256:1f281be267402e83… · /containers/cna/metrics/0/cvssV3_1
{"metric":{"attackComplexity":"HIGH","attackRequirements":"NONE","attackVector":"NETWORK","baseScore":6.3,"baseSeverity":"MEDIUM","privilegesRequired":"NONE","subAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"LOW","userInteraction":"NONE","vectorString":"CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:L/SA:N","version":"4.0","vulnAvailabilityImpact":"NONE","vulnConfidentialityImpact":"LOW","vulnIntegrityImpact":"LOW"},"metric_type":"cvssV4_0"}
  • cve_program_cvelist_v5cvss
    urn:baitaphish:normalized-source-record:v2:c759effd3c5dcdd57c65dfef784205ce91fa66e11e27d475f498db7f98a71b54 · sha256:1f281be267402e83… · /containers/cna/metrics/1/cvssV4_0

CWE assertions

1 source assertion
{"cweId":"CWE-444","description":"Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')","lang":"en","type":"CWE"}
  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:c759effd3c5dcdd57c65dfef784205ce91fa66e11e27d475f498db7f98a71b54 · sha256:1f281be267402e83… · /containers/cna/problemTypes/0/descriptions/0

Source references

3 source assertions
{"name":"Proof of Concept","tags":["exploit","third-party-advisory"],"url":"https://github.com/bikini/exploitarium/tree/main/nghttp2-nghttpx-upgrade-queue-poison-poc"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:c759effd3c5dcdd57c65dfef784205ce91fa66e11e27d475f498db7f98a71b54 · sha256:1f281be267402e83… · /containers/cna/references/0
{"name":"Fix commit (master)","tags":["patch"],"url":"https://github.com/nghttp2/nghttp2/commit/ab28105c4a0197da24f8bfc414bc116055249e1e"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:c759effd3c5dcdd57c65dfef784205ce91fa66e11e27d475f498db7f98a71b54 · sha256:1f281be267402e83… · /containers/cna/references/1
{"name":"VulnCheck Advisory: nghttp2 nghttpx - HTTP Request/Response Smuggling via Upgrade Request with Content-Length","tags":["third-party-advisory"],"url":"https://www.vulncheck.com/advisories/nghttp2-nghttpx-http-request-response-smuggling-via-upgrade-request-with-content-length"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:c759effd3c5dcdd57c65dfef784205ce91fa66e11e27d475f498db7f98a71b54 · sha256:1f281be267402e83… · /containers/cna/references/2

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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