Skip to main content
CVE-2026-109584VulnerabilityPublished Updated

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

0
Authoritative record:CVE-2026-109584· High 8.7

Not known to be exploited · CVSS 8.7 High.

Data as of 28 Oct 2026, 22:31 UTC

CVSS 4.0 base score
8.7High
How severe the flaw is on the 0–10 CVSS scale.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 26 Oct 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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

ProductAffectedFixed in
Ubuntu 26.10banditpkg:deb/ubuntu/bandit?arch=source&distro=stonkingOther threatsAffected
  • =1.7.10-3
  • =1.9.4-1
Fixed in–
Ubuntu 26.04 LTSbanditpkg:deb/ubuntu/bandit?arch=source&distro=resoluteOther threatsAffected
  • =1.7.10-2
  • =1.7.10-3
Fixed in–
Ubuntu 24.04 LTSbanditpkg:deb/ubuntu/bandit?arch=source&distro=nobleOther threatsAffected
  • =1.6.2-3
Fixed in–
Ubuntu 22.04 LTSbanditpkg:deb/ubuntu/bandit?arch=source&distro=jammyOther threatsAffected
  • =1.6.2-1
Fixed in–
Ubuntu 20.04 LTSbanditpkg:deb/ubuntu/bandit?arch=source&distro=focalOther threatsAffected
  • =1.5.1-3
  • =1.6.2-1
Fixed in–
Ubuntu 18.04 LTSbanditpkg:deb/ubuntu/bandit?arch=source&distro=bionicOther threatsAffected
  • =1.4.0-0ubuntu2
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

Community reviews

Loading reviews…