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VulnerabilityPublished

CVE-2026-59248: ninenines cowlib · Unthrottled Resource Allocation

Affects ninenines cowlibSource CVE Database V5

0

Not known to be exploited · CVSS 8.7 High : upgrade to 2.19.0 soon.

Data as of 27 Oct 2026, 05:11 UTC

CVSS 4.0 base score
8.7High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.2% chance of exploitation in 30 days – higher than 21% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 2.19.0, f582430498072a0c65ad338030321576dc13a343
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 28 Jul 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

Upgrade cowlib to 2.19.0; cowlib to f582430498072a0c65ad338030321576dc13a343.

Affected software

ProductAffectedFixed in
nineninescowlibAffected
  • >=2.0.0-pre.1 <2.19.0
Fixed in
  • 2.19.0
nineninescowlibAffected
  • ≥ 5ddecbc121f812aec53d9df91829448d8e94e44c, < f582430498072a0c65ad338030321576dc13a343
Fixed in
  • f582430498072a0c65ad338030321576dc13a343
Hexcowlibpkg:hex/cowlibOther threatsAffected
  • >=2.0.0-pre.1 <2.19.0
Fixed in
  • 2.19.0

CPE configurations (1)

  • cpe:2.3:a:ninenines:cowlib:*:*:*:*:*:*:*:*

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

If you cannot patch yet, consider limiting exposure of endpoints that accept HPACK or QPACK from untrusted peers or applying network-level protections to mitigate potential denial of service attempts.

Description

Allocation of resources without limits vulnerability in ninenines cowlib allows an unauthenticated remote HTTP/2 or HTTP/3 peer to exhaust memory on the vulnerable server (or client) and cause a denial of service. The HPACK and QPACK prefixed-integer decoder cow_hpack_common:dec_big_int/3 in src/cow_hpack_common.hrl (invoked from cow_hpack:decode/2 in src/cow_hpack.erl and from cow_qpack:decode_field_section/3 in src/cow_qpack.erl) reads continuation octets until it sees one whose high bit is clear, evaluating Int + (Value bsl M) at each step with the shift M growing by seven per octet. No limit is enforced on the number of continuation octets, on the resulting bit width, or on the value; the decoder consumes whatever encoded length the peer supplies. Because Erlang integers are immutable, each intermediate Value bsl M and each accumulator update allocates a fresh bignum whose digit width grows linearly with the number of octets processed so far. Summed across the whole decode, the transient bignum digit materialization is on the order of the square of the encoded length. A single maximal HPACK indexed representation carried inside one HTTP/2 HEADERS plus one CONTINUATION frame at Cowboy's default max_frame_size_received can force hundreds of megabytes of transient allocation and garbage-collection churn before the resulting header-table index is rejected as invalid. Repeated or concurrent connections multiply the pressure and can drive the Erlang VM to memory exhaustion. Cowlib is the HTTP parser used by Cowboy, RabbitMQ's management plugin, and other Erlang and Elixir HTTP/2 and HTTP/3 servers and clients, so any exposed endpoint that accepts HPACK or QPACK from an untrusted peer is reachable. This issue affects cowlib: from 2.0.0 before 2.19.0.

References

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