Improper Handling of Highly Compressed Data (Data Amplification) vulnerability in the HTTP/2 implementation of mtrudel bandit allows an unauthenticated remote attacker to exhaust server memory via a small HPACK-compressed HEADERS block
Affects banditSource GCVE Database
Not known to be exploited · CVSS 8.7 High.
Data as of 28 Oct 2026, 22:31 UTC
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:NExploitation evidence
Disclosed: evidence found.
CVE published 26 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 26.10banditpkg:deb/ubuntu/bandit?arch=source&distro=stonkingOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSbanditpkg:deb/ubuntu/bandit?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 24.04 LTSbanditpkg:deb/ubuntu/bandit?arch=source&distro=nobleOther threats | Affected
| Fixed in– |
Ubuntu 22.04 LTSbanditpkg:deb/ubuntu/bandit?arch=source&distro=jammyOther threats | Affected
| Fixed in– |
Ubuntu 20.04 LTSbanditpkg:deb/ubuntu/bandit?arch=source&distro=focalOther threats | Affected
| Fixed in– |
Ubuntu 18.04 LTSbanditpkg:deb/ubuntu/bandit?arch=source&distro=bionicOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
Description
Improper Handling of Highly Compressed Data (Data Amplification) vulnerability in the HTTP/2 implementation of mtrudel bandit allows an unauthenticated remote attacker to exhaust server memory via a small HPACK-compressed HEADERS block. The block stores one large cookie value in the HPACK dynamic table and then references it tens of thousands of times with 1-byte indexed fields. In the reporter's run, a 49 KB block made a server with default settings allocate a 183 MB cookie binary before any application code ran, and every concurrent stream can repeat the cost. Bandit.HTTP2.Connection caps only the compressed block (max_header_block_size), and its check of the decoded list against max_header_list_size never fires because that setting defaults to :infinity. combine_cookie_crumbs/1 in lib/bandit/http2/stream.ex then joins every crumb into one binary. This issue affects bandit: from 0.3.3 before 1.14.0.
References
- ubuntu.com/security/CVE-2026-109584 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-109584 (opens in a new tab)
- cna.erlef.org/cves/cve-2026-109584.html (opens in a new tab)
- github.com/mtrudel/bandit/commit/220b9dfd27f9a21305be2afc75cbe585ddc24e7a (opens in a new tab)
- github.com/mtrudel/bandit/commit/44bf969cd59851622fb6ee4d16227fbc39a77fb4 (opens in a new tab)
- github.com/mtrudel/bandit/security/advisories/ghsa-7gfj-7gvq-3xqj (opens in a new tab)
- hex.pm/packages/bandit (opens in a new tab)
- github.com (opens in a new tab)
- github.com/mtrudel/bandit (opens in a new tab)
- repo.hex.pm (opens in a new tab)
- github.com/cveproject/cvelistv5/tree/main/cves/2026/109xxx/cve-2026-109584.json (opens in a new tab)
- nvd.nist.gov/vuln/detail/cve-2026-109584 (opens in a new tab)
- osv.dev/vulnerability/eef-cve-2026-109584 (opens in a new tab)