CVEsmtrudelCVE-2026-110499Published Oct 26, 13:32 · Updated Oct 26, 15:35 UTC
8.7
HighCVSS 4.0 · from EEF
CVE-2026-110499

Client-chosen HPACK encoder table size is applied uncapped, growing per-connection state with every response in Bandit

bandit · Allocation without limits · CWE-770
Affectedbandit, mtrudel/bandit
FixUpdate to 1.14.0, 220b9dfd27f9a21305be2afc75cbe585ddc24e7a or newer
PublishedOct 26, 13:32 · EEF
ScoredOct 26 · 8.7 · EEF
Exploit code publicNone known · checked 21:18 UTC
ExploitedNone known · CISA KEV checked 22:10 UTC

What we know

No known exploitation. CISA KEV, checked 22:10 UTC.
No public exploit code known. Exploit-DB, Metasploit, Nuclei, checked 21:18 UTC.
An attacker only needs network access to the target. No login needed. CVSS: network, no privileges.
A successful attack can take the service down. CVSS impact.

Description

Allocation of Resources Without Limits or Throttling vulnerability in the HTTP/2 implementation of mtrudel bandit allows an unauthenticated remote attacker to grow per-connection memory and CPU cost without bound via a large SETTINGS_HEADER_TABLE_SIZE. Bandit resizes its HPACK encoder table to whatever size the client advertises, up to 2^32-1 bytes, and indexes response headers into it. Because responses carry distinct values such as date or content-length, nothing is evicted and the table grows with every response for the life of the connection, while each lookup scans it linearly. The SETTINGS handling in Bandit.HTTP2.Connection (lib/bandit/http2/connection.ex) passes remote_settings.header_table_size to HPAX.resize/2 with no server-side cap, and encode_headers encodes every response header as :store. Serving N responses on one connection therefore costs O(N²) CPU in the connection process. This issue affects bandit: from 0.3.6 before 1.14.0.

From EEF

Affected and fixed versions

ProductAffectedFixed inbandit0.3.6 – before 1.14.01.14.0mtrudel/bandit0e68313fab9d204257ebad5c447e4cd9cea8e0ea – before 220b9dfd27f9a21305be2afc75cbe585ddc24e7a220b9dfd27f9a21305be2afc75cbe585ddc24e7a

Exploit code

Exploit-DBnone knownMetasploitnone knownNucleinone known

References

Client-chosen HPACK encoder table size is applied uncapped, growing per-connection state with every response in Bandit · github.comvendor advisoryrelatedEEF CNA record for CVE-2026-110499 · cna.erlef.orgrelatedOSV record EEF-CVE-2026-110499 · osv.devrelatedIntroducing commit 0e68313 in mtrudel/bandit · github.comrelatedFix commit 220b9df in mtrudel/bandit · github.compatch

Other CVEs in bandit

All 23 →
8.7HTTP/2 request bodies made of 1-byte DATA frames amplify memory use in Bandit · CVE-2026-116078Oct 288.7SETTINGS and stream-0 WINDOW_UPDATE frames trigger quadratic work over blocked streams in Bandit · CVE-2026-108529Oct 268.7HTTP/2 cookie crumb join expands a small HPACK header block into an unbounded allocation in Bandit · CVE-2026-109584Oct 26