From 82b7c9c35aaebf8a2811bdb703dd51c2fa0693c2 Mon Sep 17 00:00:00 2001
From: Philippe Antoine <pantoine@oisf.net>
Date: Wed, 18 Feb 2026 16:40:23 +0100
Subject: [PATCH] http2: bound number of http2 frames per tx

Ticket: 8289

If stream.reassembly.depth is unlimited,
an attacker controlling the 2 sides of a communication going through Suricata
can send a transition with an infinite number of headers, until suricata OOMs

Solution is to offer a configuration option to bound the number
of HTTP2 frames we store in a HTTP2 transaction, and produce an
anomaly if this bound is crossed

(cherry picked from commit 784e173278944c3596ea9cb219afcfafece6d156)
---
 rules/http2-events.rules |  2 ++
 rust/src/http2/http2.rs  | 23 +++++++++++++++++------
 suricata.yaml.in         |  2 ++
 3 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/rules/http2-events.rules b/rules/http2-events.rules
index 8242e2f79e..ff170e8ed6 100644
--- a/rules/http2-events.rules
+++ b/rules/http2-events.rules
@@ -22,3 +22,5 @@ alert http2 any any -> any any (msg:"SURICATA HTTP2 authority host mismatch"; fl
 alert http2 any any -> any any (msg:"SURICATA HTTP2 user info in uri"; flow:established,to_server; app-layer-event:http2.userinfo_in_uri; classtype:protocol-command-decode; sid:2290014; rev:1;)
 alert http2 any any -> any any (msg:"SURICATA HTTP2 reassembly limit reached"; flow:established; app-layer-event:http2.reassembly_limit_reached; classtype:protocol-command-decode; sid:2290015; rev:1;)
 alert http2 any any -> any any (msg:"SURICATA HTTP2 data on stream zero"; flow:established; app-layer-event:http2.data_stream_zero; classtype:protocol-command-decode; sid:2290018; rev:1;)
+# disabled by default, as it can happen in legit cases depending on the max-frames config value
+# alert http2 any any -> any any (msg:"SURICATA HTTP2 too many frames"; flow:established; app-layer-event:http2.too_many_frames; classtype:protocol-command-decode; sid:2290019; rev:1;)
diff --git a/rust/src/http2/http2.rs b/rust/src/http2/http2.rs
index 008bfeb6d3..49647bc0ba 100644
--- a/rust/src/http2/http2.rs
+++ b/rust/src/http2/http2.rs
@@ -64,6 +64,7 @@ pub static mut HTTP2_MAX_TABLESIZE: u32 = 65536; // 0x10000
 // maximum size of reassembly for header + continuation
 static mut HTTP2_MAX_REASS: usize = 102400;
 static mut HTTP2_MAX_STREAMS: usize = 4096; // 0x1000
+static mut HTTP2_MAX_FRAMES: usize = 65536;
 
 #[repr(u8)]
 #[derive(Copy, Clone, PartialOrd, PartialEq, Eq, Debug)]
@@ -410,6 +411,7 @@ pub enum HTTP2Event {
     UserinfoInUri,
     ReassemblyLimitReached,
     DataStreamZero,
+    TooManyFrames,
 }
 
 pub struct HTTP2DynTable {
@@ -1067,16 +1069,18 @@ impl HTTP2State {
                     let ftype = head.ftype;
                     let sid = head.stream_id;
                     let padded = head.flags & parser::HTTP2_FLAG_HEADER_PADDED != 0;
-                    if dir == Direction::ToServer {
-                        tx.frames_ts.push(HTTP2Frame {
-                            header: head,
-                            data: txdata,
-                        });
+                    let h2frames = if dir == Direction::ToServer {
+                        &mut tx.frames_ts
                     } else {
-                        tx.frames_tc.push(HTTP2Frame {
+                        &mut tx.frames_tc
+                    };
+                    if h2frames.len() < unsafe { HTTP2_MAX_FRAMES } {
+                        h2frames.push(HTTP2Frame {
                             header: head,
                             data: txdata,
                         });
+                    } else {
+                        tx.tx_data.set_event(HTTP2Event::TooManyFrames as u8);
                     }
                     if ftype == parser::HTTP2FrameType::Data as u8 && sid == 0 {
                         tx.tx_data.set_event(HTTP2Event::DataStreamZero as u8);
@@ -1393,6 +1397,13 @@ pub unsafe extern "C" fn rs_http2_register_parser() {
                 SCLogError!("Invalid value for http2.max-streams");
             }
         }
+        if let Some(val) = conf_get("app-layer.protocols.http2.max-frames") {
+            if let Ok(v) = val.parse::<usize>() {
+                HTTP2_MAX_FRAMES = v;
+            } else {
+                SCLogError!("Invalid value for http2.max-frames");
+            }
+        }
         if let Some(val) = conf_get("app-layer.protocols.http2.max-table-size") {
             if let Ok(v) = val.parse::<u32>() {
                 HTTP2_MAX_TABLESIZE = v;
diff --git a/suricata.yaml.in b/suricata.yaml.in
index 3cc45a461f..b891e76461 100644
--- a/suricata.yaml.in
+++ b/suricata.yaml.in
@@ -969,6 +969,8 @@ app-layer:
       #max-table-size: 65536
       # Maximum reassembly size for header + continuation frames
       #max-reassembly-size: 102400
+      # Maximum number of frames per tx
+      #max-frames: 65536
     smtp:
       enabled: yes
       raw-extraction: no