{"id":"GHSA-6jqx-86gh-f27w","summary":"Netty SPDY SETTINGS frame count materializes unbounded settings map","details":"### Summary\nNetty's SPDY SETTINGS decoder accepts a peer-declared SETTINGS entry count up to the 24-bit frame-length limit and materializes every unique setting ID in `DefaultSpdySettingsFrame` without an implementation-level count cap. A remote SPDY/3.1 peer can send one syntactically valid roughly 2 MiB SETTINGS frame that creates 262144 map entries, amplifying network input into heap growth and ordered-map insertion work.\n\n### Details\nInbound SPDY bytes enter `SpdyFrameCodec.decode()` and are passed directly to the frame decoder. The decoder reads the peer-controlled flags and 24-bit frame length from the common header, then accepts SETTINGS frames with only `length \u003e= 4`. For SETTINGS payloads, it reads the peer-controlled `numSettings` field and validates only that the remaining payload is divisible into 8-byte entries and exactly matches that count. Each accepted entry then supplies an attacker-controlled 24-bit ID and value, and the normal delegate path forwards it into `spdySettingsFrame.setValue()`. The sink is `DefaultSpdySettingsFrame`: it backs settings with a `TreeMap`, checks only that IDs fit the SPDY 24-bit maximum, and inserts a new `Setting` for each previously unseen ID. There is no count budget between the wire-format count validation and the TreeMap insertion site.\n\n### PoC\n[poc.zip](https://github.com/user-attachments/files/28445737/poc.zip)\n\nrun with\n```bash\nbash ./poc/run.sh\n```\n\nexpected output:\n```text\nNETTY_SPDY_SETTINGS_COUNT_MAP_TRIGGERED settings_count=262144 wire_bytes=2097164 approx_heap_delta=17692272 first_value=1 last_value=262144\n```\n\nThe `NETTY_SPDY_SETTINGS_COUNT_MAP_TRIGGERED` line means the harness decoded the crafted SETTINGS frame and observed all 262144 peer-selected IDs in the resulting settings map. The `wire_bytes=2097164`, `first_value=1`, and `last_value=262144` fields distinguish this from a setup failure: they show the exact oversized frame was accepted and fully materialized.\n\n### Impact\n remote unauthenticated network peer that can speak SPDY/3.1 to a Netty pipeline containing `SpdyFrameCodec` can trigger resource-exhaustion denial of service. The required guards are satisfied by a complete valid SETTINGS frame using the expected SPDY version, a length of `4 + numSettings * 8`, and IDs within the accepted 24-bit range; the verified PoC uses `numSettings=262144` and `wire_bytes=2097164`. On that input, Netty materializes 262144 attacker-controlled entries in a TreeMap-backed `DefaultSpdySettingsFrame`, with local runs observing about 17-18 MiB of heap growth per decoded frame plus CPU work for ordered-map insertion.","aliases":["CVE-2026-55831"],"modified":"2026-07-22T21:15:31.909218444Z","published":"2026-07-22T21:07:36Z","database_specific":{"github_reviewed":true,"github_reviewed_at":"2026-07-22T21:07:36Z","nvd_published_at":"2026-07-21T00:17:35Z","cwe_ids":["CWE-400"],"severity":"HIGH"},"references":[{"type":"WEB","url":"https://github.com/netty/netty/security/advisories/GHSA-6jqx-86gh-f27w"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-55831"},{"type":"WEB","url":"https://github.com/netty/netty/commit/5b68c61f37aa4a3045cba624cbea239655c9003b"},{"type":"WEB","url":"https://github.com/netty/netty/commit/bb2ff68a1fb71cb4b0eb9a9e17b66c52aff680c6"},{"type":"PACKAGE","url":"https://github.com/netty/netty"},{"type":"WEB","url":"https://github.com/netty/netty/releases/tag/netty-4.1.136.Final"},{"type":"WEB","url":"https://github.com/netty/netty/releases/tag/netty-4.2.16.Final"}],"affected":[{"package":{"name":"io.netty:netty-codec-http","ecosystem":"Maven","purl":"pkg:maven/io.netty/netty-codec-http"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"4.2.0.Final"},{"fixed":"4.2.16.Final"}]}],"versions":["4.2.0.Final","4.2.1.Final","4.2.10.Final","4.2.11.Final","4.2.12.Final","4.2.13.Final","4.2.14.Final","4.2.15.Final","4.2.2.Final","4.2.3.Final","4.2.4.Final","4.2.5.Final","4.2.6.Final","4.2.7.Final","4.2.8.Final","4.2.9.Final"],"database_specific":{"last_known_affected_version_range":"\u003c= 4.2.15.Final","source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-6jqx-86gh-f27w/GHSA-6jqx-86gh-f27w.json"}},{"package":{"name":"io.netty:netty-codec-http","ecosystem":"Maven","purl":"pkg:maven/io.netty/netty-codec-http"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"4.1.0.Final"},{"fixed":"4.1.136.Final"}]}],"versions":["4.1.0.Final","4.1.1.Final","4.1.10.Final","4.1.100.Final","4.1.101.Final","4.1.102.Final","4.1.103.Final","4.1.104.Final","4.1.105.Final","4.1.106.Final","4.1.107.Final","4.1.108.Final","4.1.109.Final","4.1.11.Final","4.1.110.Final","4.1.111.Final","4.1.112.Final","4.1.113.Final","4.1.114.Final","4.1.115.Final","4.1.116.Final","4.1.117.Final","4.1.118.Final","4.1.119.Final","4.1.12.Final","4.1.120.Final","4.1.121.Final","4.1.122.Final","4.1.123.Final","4.1.124.Final","4.1.125.Final","4.1.126.Final","4.1.127.Final","4.1.128.Final","4.1.129.Final","4.1.13.Final","4.1.130.Final","4.1.131.Final","4.1.132.Final","4.1.133.Final","4.1.134.Final","4.1.135.Final","4.1.14.Final","4.1.15.Final","4.1.16.Final","4.1.17.Final","4.1.18.Final","4.1.19.Final","4.1.2.Final","4.1.20.Final","4.1.21.Final","4.1.22.Final","4.1.23.Final","4.1.24.Final","4.1.25.Final","4.1.26.Final","4.1.27.Final","4.1.28.Final","4.1.29.Final","4.1.3.Final","4.1.30.Final","4.1.31.Final","4.1.32.Final","4.1.33.Final","4.1.34.Final","4.1.35.Final","4.1.36.Final","4.1.37.Final","4.1.38.Final","4.1.39.Final","4.1.4.Final","4.1.40.Final","4.1.41.Final","4.1.42.Final","4.1.43.Final","4.1.44.Final","4.1.45.Final","4.1.46.Final","4.1.47.Final","4.1.48.Final","4.1.49.Final","4.1.5.Final","4.1.50.Final","4.1.51.Final","4.1.52.Final","4.1.53.Final","4.1.54.Final","4.1.55.Final","4.1.56.Final","4.1.57.Final","4.1.58.Final","4.1.59.Final","4.1.6.Final","4.1.60.Final","4.1.61.Final","4.1.62.Final","4.1.63.Final","4.1.64.Final","4.1.65.Final","4.1.66.Final","4.1.67.Final","4.1.68.Final","4.1.69.Final","4.1.7.Final","4.1.70.Final","4.1.71.Final","4.1.72.Final","4.1.73.Final","4.1.74.Final","4.1.75.Final","4.1.76.Final","4.1.77.Final","4.1.78.Final","4.1.79.Final","4.1.8.Final","4.1.80.Final","4.1.81.Final","4.1.82.Final","4.1.83.Final","4.1.84.Final","4.1.85.Final","4.1.86.Final","4.1.87.Final","4.1.88.Final","4.1.89.Final","4.1.9.Final","4.1.90.Final","4.1.91.Final","4.1.92.Final","4.1.93.Final","4.1.94.Final","4.1.95.Final","4.1.96.Final","4.1.97.Final","4.1.98.Final","4.1.99.Final"],"database_specific":{"last_known_affected_version_range":"\u003c= 4.1.135.Final","source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-6jqx-86gh-f27w/GHSA-6jqx-86gh-f27w.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"}]}