SETTINGS and stream-0 WINDOW_UPDATE frames trigger quadratic work over blocked streams in Bandit
Impact
Bandit versions 0.3.4 before 1.14.0 have an Inefficient Algorithmic Complexity vulnerability, allowing an unauthenticated remote attacker to exhaust server CPU via small SETTINGS or WINDOW_UPDATE frames. The attacker can open thousands of blocked streams and send frames that make the server perform quadratic work. This issue affects the HTTP/2 implementation.
Summarized by @cf/meta/llama-3.3-70b-instruct-fp8-fast. Verify details against the original sources.What to do
From 1.9.0, bound the number of streams a client can open, for example with http_2_options: [default_local_settings: [max_concurrent_streams: 100]], which bounds the work each frame can cause. From 0.7.0, disabling HTTP/2 with http_2_options: [enabled: false] removes the vulnerable path.
Affected packages
Affected products
Vendor version evidence. Product records are separate from automatic dependency matching.
mtrudel · EEF
bandit
1 range
mtrudel · EEF
bandit
Package identity
pkg:hex/banditExplore bandit →Identity supplied by EEF. Version matching requires compatible range evidence.
Compare with this publisher’s ranges. This does not inspect your installation.
affected
0.3.4 → before 1.14.0
semver versions
Other versions: unaffected
Product identifiers (CPE)
cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*mtrudel · EEF
bandit
1 range
mtrudel · EEF
bandit
Package identity
pkg:github/mtrudel/banditIdentity supplied by EEF. Version matching requires compatible range evidence.
Compare with this publisher’s ranges. This does not inspect your installation.
affected
6feadb31189d18b7dcda6c663112cd3bbaf63a46 → before 220b9dfd27f9a21305be2afc75cbe585ddc24e7a
git versions
Other versions: unaffected
Product identifiers (CPE)
cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*Original source description
Inefficient Algorithmic Complexity vulnerability in the HTTP/2 implementation of mtrudel bandit allows an unauthenticated remote attacker to exhaust server CPU via small SETTINGS or connection-level WINDOW_UPDATE frames. The attacker opens thousands of streams whose responses block on the connection send window, then sends cheap frames that each make the server walk the whole queue of blocked sends. In the reporter's run, with 3,000 blocked streams a single 9-byte SETTINGS frame took 133 ms to process.
do_pending_sends/2 in lib/bandit/http2/connection.ex retries every queued send and, before each retry, removes that entry from the queue with List.delete/2, so one frame costs O(n²) list operations for n blocked streams. max_concurrent_streams defaults to :infinity, so the attacker chooses n.
This issue affects bandit: from 0.3.4 before 1.14.0.
Inside the record
Evidence available
Describes the evidence in this view, not whether the product is safe.
Original records
CVE-2026-108529View the latest unmodified CVE JSON from the official source. It may be newer than this imported page.
cve.new JSON →Underlying weaknesses
The source’s classification of what caused the vulnerability.
Environment requirements
These conditions apply together as specified by the publisher. A matching product name alone does not establish exposure.
EEF · platform conditions
All conditions must hold
Any condition may hold
Vulnerable product
cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*From (inclusive): 0.3.4
Before: 1.14.0
Original applicability statements
[
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*",
"versionEndExcluding": "1.14.0",
"versionStartIncluding": "0.3.4",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
],
"operator": "AND"
}
]Contributing organizations · 2
Assigning organization
Additional data publisher
What changed
Follow changesLarge field values are marked as truncated previews. Original source snapshots remain retained.