CVE Explorer

CVE-2026-54340

h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. Prior to commit 9265bdd, there is an HTTP/2 state amplification issue that combines HPACK decompression amplification with Slowloris-style stream stalling. Amplified decoded header state can be retained by stalled HTTP/2 streams, and depending on the configuration, additional limits are needed to bound decoded header state and prevent attack. This issue has been fixed by commit 9265bdd.

Lifecycle PUBLISHED1 preserved revisionFact urn:baitaphish:canonical-cve-fact-revision:v2:b909af5c86a825768e74108bf25aa0b9be86cfd4b364ef98ac5eb03ce0458c95

Known exploited

Not asserted

Disputed

Stale source

Conflicts

Preserved source conflicts

No provider value was silently selected as the winner.

cwe · 2 assertions

{"cweId":"CWE-400","description":"CWE-400: Uncontrolled Resource Consumption","lang":"en","type":"CWE"}

cve_program_cvelist_v5cwe
urn:baitaphish:normalized-source-record:v2:7b2651eff14bb34911a38fd4d77f37460c1e2779574cdfd2541ec5958a60302c · sha256:377aa9b5c4cc2a88… · /containers/cna/problemTypes/0/descriptions/0

{"cweId":"CWE-770","description":"CWE-770: Allocation of Resources Without Limits or Throttling","lang":"en","type":"CWE"}

cve_program_cvelist_v5cwe
urn:baitaphish:normalized-source-record:v2:7b2651eff14bb34911a38fd4d77f37460c1e2779574cdfd2541ec5958a60302c · sha256:377aa9b5c4cc2a88… · /containers/cna/problemTypes/1/descriptions/0

Affected products and versions

1 source assertion

{"product":"h2o","vendor":"h2o","versions":[{"status":"affected","version":"< 9265bdd"}]}

cve_program_cvelist_v5affected
urn:baitaphish:normalized-source-record:v2:7b2651eff14bb34911a38fd4d77f37460c1e2779574cdfd2541ec5958a60302c · sha256:377aa9b5c4cc2a88… · /containers/cna/affected/0

Provider-owned CVSS observations

1 source assertion

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

cve_program_cvelist_v5cvss
urn:baitaphish:normalized-source-record:v2:7b2651eff14bb34911a38fd4d77f37460c1e2779574cdfd2541ec5958a60302c · sha256:377aa9b5c4cc2a88… · /containers/cna/metrics/0/cvssV3_1

CWE assertions

2 source assertions

{"cweId":"CWE-400","description":"CWE-400: Uncontrolled Resource Consumption","lang":"en","type":"CWE"}

cve_program_cvelist_v5cwe
urn:baitaphish:normalized-source-record:v2:7b2651eff14bb34911a38fd4d77f37460c1e2779574cdfd2541ec5958a60302c · sha256:377aa9b5c4cc2a88… · /containers/cna/problemTypes/0/descriptions/0

{"cweId":"CWE-770","description":"CWE-770: Allocation of Resources Without Limits or Throttling","lang":"en","type":"CWE"}

cve_program_cvelist_v5cwe
urn:baitaphish:normalized-source-record:v2:7b2651eff14bb34911a38fd4d77f37460c1e2779574cdfd2541ec5958a60302c · sha256:377aa9b5c4cc2a88… · /containers/cna/problemTypes/1/descriptions/0

Source references

2 source assertions

{"name":"https://github.com/h2o/h2o/commit/9265bdd9a996ed992681055e3996baf3e09d2063","tags":["x_refsource_MISC"],"url":"https://github.com/h2o/h2o/commit/9265bdd9a996ed992681055e3996baf3e09d2063"}

cve_program_cvelist_v5reference
urn:baitaphish:normalized-source-record:v2:7b2651eff14bb34911a38fd4d77f37460c1e2779574cdfd2541ec5958a60302c · sha256:377aa9b5c4cc2a88… · /containers/cna/references/1

{"name":"https://github.com/h2o/h2o/security/advisories/GHSA-qcrr-wrhc-pgq9","tags":["x_refsource_CONFIRM"],"url":"https://github.com/h2o/h2o/security/advisories/GHSA-qcrr-wrhc-pgq9"}

cve_program_cvelist_v5reference
urn:baitaphish:normalized-source-record:v2:7b2651eff14bb34911a38fd4d77f37460c1e2779574cdfd2541ec5958a60302c · sha256:377aa9b5c4cc2a88… · /containers/cna/references/0

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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